The development of pre-Qin legalists probably went through four stages: first, the budding stage. The emergence of Legalism can be traced back to Guan Zhong and Zi Chan in the Spring and Autumn Period. People usually regard them as the pioneers of legalism. In fact, there is no legalist in the strict sense at this time, which can only be regarded as the embryonic period of legalism. The second is the founding stage. The real founders of Legalism are Li Kui, Wuqi, Shang Yang, Shen Buhai and Shen Dao. Legalists in the founding period formed their own characteristics: first, most of them personally participated in the wave of political reform in various countries at that time and became the actual leaders of the political reform movement. Secondly, attach importance to economic development, especially agricultural production. Third, the legalists' harsh laws have gone to extremes in the initial stage, especially Wuqi and Shang Yang, who pursued a despicable and not so generous policy of "breaking the law, kissing and respecting kindness". The third is the mature stage. The final establishment of legalism should be attributed to Han Fei. Han Fei is called a master of legalism because he synthesized and summarized the achievements and lessons of the previous generation of legalists, and established the legalist thought with the unity of law, technique and emotion, thus making the legalist thought systematic. The fourth is the fading period. It can be said that the Qin Dynasty was established according to the thought pattern of Legalists, and Han Fei's thought system is the core of the Qin Dynasty's thought system. After the establishment of the Qin Dynasty, the shortcomings of Legalists were exposed very clearly. First of all, autocracy has become the core of centralized system. Secondly, it is the same autocratic line in the ideological and cultural field, which emphasizes taking law as teaching and officials as teachers. At the same time, the cruelty of its law has reached the point where it is hard to see. With the demise of the Qin Dynasty, Legalists flourished and declined, becoming martyrs, thus withdrawing from the historical stage forever as an ideological and cultural school. However, his thoughts still have a long-term and great influence on China's future political culture.