It has a history of 779 years from the unification of Sui Dynasty to Yuan Shundi's northern exile, which constitutes the second development cycle-mature stage of China feudal society. Sui Dynasty was the first dynasty in the mature stage of China feudal society. The Sui Dynasty established an important political system: three provinces and six departments. The system of three provinces-Shangshu, Menxia and Neishi-was the core of the central official system in Sui Dynasty. Although the three divisions and three publics are in the first place, they are actually only honorary positions. Sui dynasty was divided into three levels: state, county and county. Three years after the Emperor's reign, the administrative setup of the county was abolished and the county was directly controlled by the state. At the end of each year, the governor of Sui Dynasty went to Beijing to report on his work, which was called the envoy of Chao Ji. The imperial court sent officials or other envoys from Taiwan Province to inspect the provinces. The Sui Dynasty initiated a far-reaching imperial examination system. The establishment of the imperial examination system provided opportunities for civilian landlords to participate in politics and promoted the maturity of the bureaucratic system. In order to strengthen centralization and consolidate national unity, a series of systems were reorganized and established in the political, economic, legal and military systems, which had a far-reaching impact on the dynasties after the Sui Dynasty and made outstanding contributions. Compared with previous dynasties, the social economy of Sui Dynasty has also made great progress. After the establishment of the Sui Dynasty, in order to enhance national strength, some appropriate economic adjustments were made. The Sui Dynasty issued imperial edicts three times, continued to implement the system of equal land since the Northern Wei Dynasty, and made some adjustments to its specific provisions to adapt to the social exchanges at that time. In the fifth year of Emperor Yangdi, the Sui Dynasty ordered a nationwide reorganization of household registration, which dealt a blow to the economic power of the gentry, greatly increased the taxes controlled by the state, and improved the household registration system. The stable political situation promoted the prosperity of social economy and strengthened the national strength of Sui Dynasty. The prosperity of economy, the perfection of political system, and the high degree of national unity and centralization fully show that the feudal society in China has entered a mature stage. The Tang Dynasty after Sui Dynasty was the heyday in the development history of China feudal society. Just as Han is the policy successor of Qin State, the historical mission of Tang Dynasty is to continue the unfinished business of Sui Dynasty. Mr. Chen Yinque pointed out very accurately: "Li Tang has been handed down from generation to generation for 300 years, while Yang Sui enjoyed the country for only a short time. There is little difference in the inheritance of laws and regulations between the two dynasties, which can be regarded as one." Like the Sui Dynasty, the Central Committee of the Tang Dynasty implemented the system of three provinces and six departments. The three provinces in the Tang Dynasty were Zhongshu Province, Menxia Province and Shangshu Province. The Deputy Chief Executive of Zhongshu Province is a Zhongshu Order and Assistant Minister, and there is also a Zhongshu Sheren who is responsible for drafting the imperial edict system. The deputy chiefs of the province under the door are assistant ministers and assistant ministers, who are assigned to the Ministry and are responsible for reviewing the letters drafted by Zhongshu Province and approving the banknotes played by Shangshu Province. The deputy chief of Shangshu Province is Shangshuling and his left and right servants. The provincial government has six departments, namely, officials, households, ceremonies, soldiers, criminals and workers, which are responsible for implementing the government decrees formulated by the central government. Because Emperor Taizong used to be the minister of Shangshu, later his adjutants all avoided this position in name only, and the left and right servants actually became the highest officials of Shangshu Province. Senior officials in the three provinces in the early Tang Dynasty were all prime ministers. At that time, there was a yamen in the province under the door, where the prime ministers of the three provinces discussed military affairs. The appearance of these two tax laws marks the final maturity of feudal economy. It means that the feudal court government relaxed the personal control of farmers and reduced the super-economic exploitation. These two tax laws were formulated by Yang Yan, the prime minister of Tang Dezong era. It is a two-tax law to change the way of tax collection from collecting grain and cloth to collecting money and collecting taxes twice a year. Due to the decline of the annual land equalization system in the late Wu Dynasty, the tenancy adjustment method in the early Tang Dynasty was no longer applicable, and Tang Dezong began to implement the two tax laws in Jianzhong Yuan. The two tax laws were a major reform of China's ancient tax system, which came into being under the conditions of the collapse of the land equalization system and rent adjustment system, the rise of farmland, fake farmland, population exile, distorted household registration and financial difficulties of the Tang government. This tax law was very progressive at that time and produced good results. Not only did the number of government-controlled accounts increase significantly, but the tax revenue also increased significantly, which greatly improved the economic situation in the Tang Dynasty. The Tang Dynasty was the highest peak of feudal society in China, with relatively stable politics, prosperous economy and extensive foreign exchanges. Song Dynasty is an era in the history of China, which inherited the Five Dynasties and Ten Countries and initiated the Yuan Dynasty. Divided into Northern Song Dynasty and Southern Song Dynasty. In 960, Zhao Kuangyin, a general at the end of the Zhou Dynasty, was awarded the yellow robe to establish the Song Dynasty. The period of Zhenzong and Renzong entered a prosperous time, and the centralization of power was strengthened in the early Northern Song Dynasty, which solved the problem of separatist regime in the buffer regions. There was a social crisis in the middle period, and Wang Anshi's political reform eased. Wang Anshi's new law includes equal damage, young crops, exemption from service, Yishi, Jiabao, Ma Bao and other land taxes. The political system of the Song Dynasty generally followed the political system of the Tang Dynasty. But the prime minister is no longer the chief executive of the three provinces, and the other is a matter of peace under the same book. It also added a deputy minister who participated in government affairs, commonly known as ruling, and collectively referred to as "slaughter" with the prime minister. In the Song Dynasty, the relative power was greatly reduced, and it was only responsible for administrative functions. Zhongshumen and Privy Council are collectively called the Second House, which is in charge of civil affairs and military affairs. There are also three divisions: Salt and Iron Division, Household Division and Expenditure Division, which are in charge of financial power. In this way, the three powers, namely, the three secretaries, the generals and the Tang Dynasty, balanced each other, thus weakening the relative power and strengthening the imperial power. In Song Dynasty, an admonition court and an admonition officer were set up outside Yushitai, which were the supervisory bodies responsible for impeachment and other affairs. In order to strengthen centralization and prevent the generals from seizing power, Song Taizu cut off the important position of censor and cancelled the military power of military attache. The leading bodies of the Imperial Army were changed to the Front Department and the Guard Department, which were respectively commanded by the Front Department, the Step Army and the Ma Army. Set up a Privy Council in the central government to take charge of the military. The Privy Council is directly responsible to the emperor, and other officials are not allowed to ask. The deployment of troops in the Song Dynasty can be described as "strong cadres and weak branches" and "internal weakness and external defense". There were four kinds of armies in the Song Dynasty, namely, the imperial army, the Xiang army, the township army and the Francisco army. The imperial army is the central army and the main force of Song Jun. Xiang army is a town soldier in each state and is controlled by the local governor. Rural soldiers are able-bodied men transferred by the authorities. Fan Bing is a frontier army of non-Han nationality. The emergence of "jiaozi" is the result of commodity exchange prosperity and market expansion. Accordingly, the ancient civilization of China reached a high development stage in the Tang Dynasty. However, the maturity of feudal culture, the formation of feudal cultural climax is not in the Tang Dynasty, but in the Song Dynasty, because the highest realm of civilization is not poetry, but philosophy. Hagen once said when talking about the characteristics of philosophy: "When the city-state of Ionia in Asia Minor declined, Ionia's philosophy also rose." "In Athens, due to the deterioration of young people's lives, the period of philosophical prosperity has arrived", which seems to be completely in line with China's national conditions. When the prosperity and economy of the prosperous Tang Dynasty began to decline with the separatist regime of the buffer region, Zhu Cheng Neo-Confucianism, which reflected the essence of this life, began to rise in the poor and weak Song Dynasty and ruled China for nearly seven centuries. Song Dynasty was the golden age in the history of China, with unprecedented development of national integration and commodity economy, frequent foreign exchanges and rapid development of culture and art. Yuan Dynasty was the first unified dynasty established by ethnic minorities in China history. Kublai Khan carried out "Chinese law", attached importance to agricultural economy and protected agricultural production. Strengthen centralization in politics, weaken the power of Mongolian nobles, and turn nobles into fields. Although the implementation of "Chinese law" was accompanied by the sharp struggle between reformists and conservatives in Mongolian aristocrats, and even led to bloody conflicts, it weakened the backward factors of Mongolians themselves and accelerated the feudalization of Mongolians. The rulers of the Yuan Dynasty also received more extensive support and cooperation from the Han landlord class, which was conducive to the consolidation of the rule of the Yuan Dynasty and social progress. The unification of the Yuan Dynasty finally formed the second national and cultural fusion in Chinese history. This kind of fusion and convergence is much greater than the first time. Its national integration includes Arabs in Central Asia, and its cultural convergence includes Arab culture and European culture. Moreover, this kind of integration and cohesion is more stable and in-depth. To sum up, from the political, economic, cultural, military and many other aspects, it can be concluded that the Sui, Tang, Song and Yuan Dynasties were the mature stage of China feudal society.