This paper conducts empirical analysis, using the trade data and EIA database among 170 countries from 1996 to 2017. Estimation results show that, trade agreements mainly increase the trade volume through extensive margin and quantity, and there is no effect on price. Further research also finds that the effects of trade agreements differ in different degrees of trade liberalization and terms of trade, types of importing and exporting countries and the institution quality gap. The conclusions of this paper remain robust after considering endogeneity issues, zero trade and other factors. The above conclusions indicate that while affirming the volume effect of trade agreements, the quality effect of trade agreements should be treated with caution.