Abstract: Lake chief system is an important institutional innovation in the process of water environment governance in China. It is of great practical significance to solve the problem of water pollution control and realize the sustainable utilization of lake water resources by establishing and perfecting the responsibility system of Party and government leadership as the core and implementing the responsibility of territorial management. Used the data of Wuhan Environmental Status Bulletin and Wuhan statistical yearbook from 2007 to 2017, this paper discusses the impact of Lake length system on water environment governance effect and its mechanism, and carries out a series of robustness tests on this basis. The results showed that: （1）The lake chief system significantly improves the comprehensive water quality and the total value of pollutants exceeding the standard in the pilot lakes. The above conclusion is still valid after a series of robustness tests.（2）Mechanism analysis shows that, on the one hand, the lake chief system improves the effect of water environment governance by promoting investment in environmental governance and reducing industrial sewage discharge.（3）The heterogeneity analysis shows that the lake chief system can significantly improve the water environment governance effect of the high economic level jurisdiction. Compared with the inter regional lakes, the lake chief system significantly improved the effect of non trans regional lake water environment governance. The research results provide decision-making reference for improving the lake chief system, forming a normalized and systematic water resources management system, and promoting the modernization of water environment governance system and governance capacity.