The calculation of water environmental capacity of Puzhehei lake is of great significance for preventing water pollution and protecting water ecological environment of Puzhehei Lake Basin. Based on the lack of hydrological and water quality data in Puzhehei Lake Basin, a large number of basic data were collected through pollution source investigation and water quality monitoring. On this basis, a twodimensional hydrodynamic water quality model of Puzhehei lake was established by using Mike21 model to simulate the migration and diffusion of pollutants into the lake. The current situation of pollution load in Puzhehei lake was analyzed, and the characteristics of water flow, hydrodynamic force and the migration and diffusion law of pollutants in Puzhehei Lake were analyzed. The results show that: ①the annual loads of COD, TN, TP and NH3-N in puzhehai Lake in 2018 are 4090.0t, 401.3t, 34.4t and 122.6t; ②Puzhehei lake is mainly non-point source pollution, and the difference of water environmental capacity between non rainy season and rainy season is very significant.