Combined with the development of China's economy, this paper points out the formation of pressure in the foreign exchange market, including six factors: trade friction between China and the United States, international expectation of exchange rate appreciation, huge foreign exchange reserves, interest rate difference between China and the United States, economic growth and nominal exchange rate. EMP is constructed by using the construction equation proposed by Weymark which made a general definition of the foreign exchange market pressure index. And the reason of EMP change trend is analyzed. Finally, some Suggestions are put forward to relieve the pressure of foreign exchange market.