China has reformed the exchange rate regime from pegging to the US dollar to a currency basket system since July 2005. In these two exchange rate regimes, the People’s Bank of China (PBOC) continuously intervenes in foreign exchange market. In traditional trade model, trade balance is displayed as a linear function of macroeconomic fundamentals. However, whether trade balances are influenced by central bank’s intervention and whether the trade model is a linear form are still unverified. This paper constructs smooth regime switching equation with intervention index to investigate the impact of our explanatory variables on trade model. Empirical evidences show that the trade model in U.S., Japan and E.U. do exhibit smooth regime switching in spite of different transition speeds. We find that each variable has effects on trade model vary with transition variable (intervention index) within different intervals.