Abstract: In recent years, the sewage emission in China has increased gradually and the water pollution incident happened frequently, causing serious damage to the ecological environment and residents’ health. To reverse the situation, governments at different levels have introduced various environmental protection policies. We collected weekly provincial panel data from 2013 to 2016, and three water pollution indicators including permanganate (COD_Mn), dissolved oxygen (DO) and ammonia nitrogen (NH₃) are selected. Then, differential treatment charge policy about the sewage water in Jiangsu Province were evaluated basing on the synthetic control method(SCM), and a comprehensive indicator was constructed using the entropy weight method to evaluate the comprehensive policy effect. The main findings are: the policy has obviously improved the overall surface water quality; dissolved oxygen (DO) indicator has been improved, indicating that the self-purification ability of the surface water has been improved; however, it made eutrophication increasingly serious which was measured by permanganate(COD_Mn) and ammonia nitrogen (NH₃)indicator owing to supervising difficulty. For achieving effective regulation, policy decision and its dynamic adjustment must comply with constraints of “Incentive Compatibility”.