Abstract: In order to scientifically assess the influence of Gushan Navigation and Hydropower Project construction on water environment of the upper reaches of Hanjiang River, typical days of wet, average and dry seasons were selected on the basis of runoff calculation of cascades in the upper reaches of Hanjiang River, one-dimensional and two-dimensional water quality models were used to analyze and predict the overall water quality, local water quality and shoreside water pollution capacity before and after the construction of Gushan Navigation and Hydropower Project under unsteady flow conditions.And the countermeasures and suggestions for water environmental protection were put forward.The results showed that average concentrations of COD and ammonia nitrogen in wet, average and dry seasons at typical sections of the reservoir area and its downstream would reduce, indicating that overall water quality would improve.However, the significant reduce of flow velocity in shoreside water would result in the deterioration of local water quality.The pollution zone of COD and ammonia nitrogen of typical sewage outlets in the reservoir area would increase in dry season.Water environment capacity of COD and ammonia nitrogen in the reservoir area would reduce by 9% and 11% respectively.To protect water environment of this reservoir area, a set of measures are proposed in the terms of domestic sewage, livestock breeding and agricultural pollution to control and prevent non-point pollution.The research results can contribute to the construction of ecological-friendly water project and the high-quality development of the Hanjiang River Ecological Economic Belt.