In order to master the variation law of dynamic water environmental capacity of urban river network, a “air-ground-water” integrated calculation model of dynamic water environmental capacity of urban river network was constructed. Taking Jinshan Lake Basin in Huizhou City, Guangdong, Hong Kong and Macao Great Bay Area as a typical area, the dynamic water environmental capacity of COD and TP in Jinshan Lake Basin in 2017 was quantitatively calculated. The results show that the relative errors of calibration and verification of flow, COD and TP concentrations simulated by the model are within 14. 04%. In 2017, the overall water environmental capacity of COD and TP in Jinshan Lake Basin increased first and then decreased, which was significantly affected by rainfall. The daily capacity variations range of COD and TP were 238. 55~3 027. 49 kg/d and 3. 73~58. 02 kg/d, respectively. The water environment capacity in dry season is small and negatively correlated with rainfall. The water environmental capacity increases obviously in heavy rain or rainstorm period in wet season. The COD capacity is negatively correlated with rainfall in moderate and light rain period, and the TP is the opposite. Ensuring ecological base flow can significantly improve the problem of insufficient capacity, and the dynamic ecological flow guarantee has an obvious effect on improving the water quality compliance rate of Jinshan Lake Basin.