According to the water quality, hydrological data of Sushui river,the paper used the blind number theory to calculate water environmental capacity and reduction of COD, NH3—N,and compared it with the results of one-dimensional steady water environmental capacity. Because of the dynamic characteristics of the river hydrology and water quality,the paper divided the Sushui river into 9 sections by using uncertain information processing method,and made the water quality and hydrological parameters into blind number.It used the calculation model of water environmental capacity under blind information to calculate the water environmental capacity and reduction of major pollutants in the river.The result indicated that the water environmental capacities of COD, NH3—N of the river are -40207 kg/d and -11675 kg/d respectively. The results are both negative indicate that they need to be reduced, the amount of reduction are 17556 kg/d and 9715 kg/d. The result which is gotten by applying blind number theory to study the water environmental capacity is more credible and has more advantages than that by deterministic calculation method.