In order to explore the economic impact of China's retaliatory tariff policy on China and the United States, this paper calculates the competitiveness of agricultural products of each country and uses GTAP model to simulate the economic changes of China and the United States. The result of this paper shows that the overall international competitiveness of American agricultural products is not high, and the increase of tariff on American agricultural products will bring greater export opportunities to Brazil, EU and ASEAN. China's tariff policy has a positive impact on China's GDP and a negative impact on the United States, but the welfare level of both countries has been reduced to varying degrees and the United States has a large reduction.