1, the change of social nature. After the Opium War, China's territory, territorial sea and judicial sovereignty were destroyed. Taking advantage of the privilege of aggression, foreign invaders frantically dumped goods and plundered raw materials in China, gradually involved the China market in the world capitalist market, and China's self-sufficient feudal economy gradually collapsed. China began to become a semi-colonial and semi-feudal society.

2. Changes in major social contradictions. The main social contradiction, from the contradiction between the landlord class and the peasant class, began to change into the contradiction between foreign capitalism and the Chinese nation, feudalism and the masses; The contradiction between foreign capitalism and the Chinese nation has become the most important contradiction among various social contradictions.

3. Changes in social revolutionary tasks (revolutionary objects). After the Opium War, the people of China shouldered the dual revolutionary task of opposing imperialist aggression and domestic feudal rule. China has since entered a long period of old democratic revolution.

Before the war, China was a politically independent country, and the Qing government could exercise its sovereignty without foreign interference. After the war, China's territorial integrity was destroyed, its sovereignty was violated in many ways, and it has lost its completely independent status.

Before the war, China was an economically independent country, and the self-sufficient feudal economy was dominant. After the war, foreign goods poured into China, and the original feudal economic base began to be destroyed. China has become a vassal of world capitalism and lost its economic independence.

Before the war, the main contradiction in China society was the contradiction between the peasant class and the landlord class; After the war, the social contradictions in China became complicated, and foreign capital-a pair of contradictions between imperialism and the Chinese nation-increased, which became more and more prominent. Comrade Mao Zedong said: "The contradiction between imperialism and the Chinese nation, feudalism and the masses of the people is the main contradiction in China society ... and the contradiction between imperialism and the Chinese nation is the most important contradiction among all kinds of contradictions." ("China Revolution and China * * * Production Party") It is precisely because of the content and form of this contradiction that the people of China began to shoulder the dual tasks of anti-imperialist and anti-feudal democratic revolution from the Opium War, which also determined the social nature of modern semi-colonial and semi-feudal society in China.

4. Harm: 1) The massive outflow of silver affected the financial management of the Qing government and made the life of working people more difficult. 2) Corrupt the ruling institutions of the Qing Dynasty; 3) weaken the combat effectiveness of the army; 4) It opened the gateway to the southeast coast of China and facilitated the invasion of foreign forces. 5) It has brought a heavy disaster to the Chinese nation.

5. Conclusion: The Opium War was an important turning point in the history of China. China society began to move from a feudal society to a semi-colonial and semi-feudal society, marking the beginning of modern China history.