Miyun Reservoir, the most important surface source water for Beijing, has been suffered water crisis due to continuous drought and over-extraction during recent years; the Central Route of South-to-North Water Diversion Project (SNWDP) is expect to transfer water from Danjiangkou Reservoir to Miyun Reservoir in order to resolve the water shortage. The SNWDP will be bound to solve release the water crisis in the respect of “water quantity”, however, the “water quality” should also be guaranteed. This project is aiming to assess the impact of the SNWDP on the water quality of Miyun Reservoir, in a view of taste & odor problem in drinking water – a long term problem in Miyun Reservoir; the laboratory simulation, field monitoring as well as model computation were performed in this project to evaluate the impact from SNWDP on the water environment, including the mixing effect between south water and reservoir water, the water environmental changes caused by the water level increase as well as the invasion of external algal species from south water. Based on these results, the environmental parameters of Miyun Reservoir were determined according to the model simulation, and the growth potential of Planktothrix sp. and the trend of taste & odor problem in Miyun Reservoir were evaluated according to ecological niche theory; this project will assess the water quality of Miyun Reservoir after the execution of SNWDP, and is believed to be helpful for scientific policy adoption and effective strategies exploration.