By applying water quality target management method this paper studied the water environmental capacity calculation and distribution of Sushui river, the key technologies of reducing pollution load, so as to reduce the emission of Sushui River pollutants. We established a hydrodynamic water quality model of Sushui River, combining with actual monitoring data, the model calibration and verification was conducted, and the environmental capacity of COD and NH3—N in the section of the water at 95%, 75% and 50% guarantee rate was investigated. The water environmental capacity of COD in the frequency year of 95%、75%、50% were -6802.037 t/a, -5891.560 t/a, -5203.764 t/a, respectively. NH3—N water environmental capacity in the frequency year of 95%,75%,50% were -3328.943 t/a, -2070.057 t/a, -1821.376 t/a respectively. It is necessary to reduce the pollutants and determine the reduction of Sushui River pollutants, the reduction of COD in extremely dry year, dry year and normal flow were 2103.75 t/a, 1926.58 t/a and 1702.33 t/a respectively, and the ammonia reduction were 927.07 t/a, 605.31 t/a, 546.29 t/a. The water quality target management technology can be used in the study of water environmental capacity of Sushui River, which can provide technical support for water quality improvement.