In order to ensure water quality control rates and the water environmental health of Wumu section in the Grand Canal, according to the water quality target of the surface water(environment) function zonation in Jiangsu province, considering factors such as hydrology , water pollution source, generalized pollution sources of the study area into the canal. Through the establishment of the study area a one-dimensional mathematical model for water quality determines the research area of water quality model parameters, calculated from the allowable discharge amount and water environment capacity of drain outlets when quality reaching the standard in Wumu section. Compared with the amount of present pollutant discharge into account, it calculated the amount of pollutants to be reduced, so as to provide basis for improving water environmental health of the Grand Canal. The results showed that, in order to ensure water quality reaching standard of Wumu section, in the near future the study area water environmental capacity of COD, NH3-N, TP were 47216, 5376.1 and 508.1 t/a respectively, in the forward water environmental capacity of COD, NH3-N, TP were 28977.3, 2319.1 and 301.1 t/a respectively. Contrast pollutant reduction rate and the excess rate of water quality which gap within 30%.The calculation results of water environment capacity are reasonable.