Study on the trade effect of Regional Trade Agreement in Service(RTAS) occurs as a result of the quickly increased signature of RTAS. Based on the bilateral data of international trade in services of OECD and classical gravity model, the paper investigates the differences in the trade effect of RTAS between China and United States, and considers the heterogeneousness of two countries with expanded data. It finds that the time effect differs: namely the trade effect of RTAS among developed countries is stren...