Using the matching panel data of Chinese industrial database and custom database in the period of 2000 to 2006, this paper studies the relationship between import competition and dual exporting margins of multi-product firm. This study finds that: (1)import competition improves the intensive and extensive margins significantly, and even stronger to the intensive margin; (2)with discretion of trade type, import competition improves the margins of processing trade more significantly than ordinary trade; (3)regression result of different industries indicates that import competition has a more significant improving effect in industries with comparative advantage. Controlling the potential endogeneity with system GMM method, the improvement of import competition on intensive and extensive margins is still robust.