Based on the data of industrial enterprises and environmental statistics, this paper constructs the panel data from 1998 to 2007, and empirically analyzes the impact of export on the SO2 emissions intensity. The regression results show that compared with non-exporters, the SO2 emissions intensity of exporters is lower; the higher the export intensity of enterprises, the lower the SO2 emissions intensity. The heterogeneity test shows that the enterprise’s export has a heterogeneity impact on SO2 emissions intensity for enterprises that are located in different regions or belonging to different industries. For the enterprises in pollution intensive manufacturing industries, the exporters are cleaner than non-exporters. The negative impact of enterprise’s export on SO2 emissions intensity in the eastern region is more significant than that in other regions. After excluding the influence of environmental regulation factors on the regression results, and through IV and PSM-DID methods to deal with endogenous problems, the regression results of this paper are still robust. The mechanism analysis shows that: on the one hand, export enterprises reduce SO2 emissions intensity by increasing the output value of new products - R D, on the other hand, by improving total factor productivity. In addition, by comparing the change of export status (extensive margin) and the change of export intensity (intensive margin), it is found that the main driving factor of low SO2 emissions intensity of export enterprises lies in the extensive margin rather than the intensive margin.