Based on an adjusted Solow economic growth model, using econometric tools such as cointegration test and Granger causality test, taking the economic factors such as foreign trade and foreign investment into account, this paper makes regression analysis on the effect of economic opening on China’s economic growth by using the data from 1985 to 2004. The analysis indicates that the domestic capital input is still the primary element that promotes China’s economic growth, by contrast, the effect of foreign trade and foreign investment is faint. It is a bidirectional causality between foreign trade and economic growth, and the adjusting velocity of trade is larger than the foreign direct investment on the balance of the China’s long-time economic growth.