Japan announced in 2013 to join the U.S.-led TPP, it will come into a larger negative impact on China's foreign trade, because China is not a member country of TPP. Using the GTAP model, this paper makes a quantitative analysis on the impact degree on China's foreign trade before and after the accession of Japan to the TPP. The results show that, after Japan joins TPP, the negative impact of China's foreign trade will be further deepened. Especially China's exports will reduce by 0.31125% and the imports wi...