Research on the Influencing Factors of Pollution Backflow Effect in River Basin

China's current water pollution intensive industries are showing a trend of upstream. If their pollutants flow downstream, which will increase the environmental risks of downstream areas. Based on the county data of the seven major river basins in China from 2004 to 2013, this paper uses 2SLS (two-stage least squares) method empirically verifies the existence of the backflow effect of pollutants. The results show that the backflow effect of pollutants is mainly caused by the competition between the upstream and downstream local governments, and the central government's environmental monitoring system for key polluting enterprises can restrain the phenomenon to a certain extent. The backflow effect of pollutants mainly occurs in domestic enterprises rather than foreign-invested ones. To control river basin pollution, the central government should carry out top-level design on the tax, financial and environmental policies of the river basin economic belt, and strictly control the environmental pollution caused by competition among local governments.