A 2-D unstable-state model of water quantity and quality on wind-driven current in Lake Taihu was established. By using the measured hydrological data the flow and concentration fields were numerically simulated, and the simulations were intercompared. Lake Zhushan was taken as a case of research area to analyze the impacts of its water environment by Zhihugang and Wujingang closing sluices, which either different wind directions or different pollutant emissions were quantificationally estimated, and the improving effects of several treatment measures were also calculated. The data showed that using 2-D unstable-state model of water quantity and quality equations to calculate showed a small measured difference for the flow and concentration fields. For the effect on water environment of Lake Zhushan, water quantity played a better role than wind directions. It would require 16 days to improve the water quality of Lake Zhushan diverting water from Yapugang River, while 25 days from Taige Canal.