Abstract: "Channel" reservoirs whose profiles are characterized as being wide and shallow, do not demonstrate gradation phenomena, so it can be assumed that pollutes entering into "channel" reservoirs mix with water completely. In this paper, the flow simulation model for "Channel" reservoirs was developed by solving one-dimensional Saint-Venant equations in Preissman weighted four-points implicit scheme and the water quality simulation model for "channel" reservoirs was developed by solving water quality equations employing the concept of full mixed reactor. The flow/water quality simulation coupled model was used to simulate the water quality situation for "channel" reservoirs. The flow/water quality simulation coupled model is of clear concept, concise structure and was used in the Guating Reservoir("Channel" reservoir) to simulate the transaction of NH₃－N with satisfied results. This model can be used for environmental impact assessment, water quality prediction and management in the Guanting Reservoir.