In order to objectively evaluate the influence of water replenishment of Taihu Lake on the improvement of the transparency of Lihu Lake,the correlation between water transparency(SD) and the concentration of suspended solids (SS) and chlorophylla (Chla) suitable for Lihu Lake was obtained by analyzing the measured data. The coupling model of hydrodynamic and water quality of Lihu Lake was constructed by using MIKE 21，which can be used for simulation and computation. The SD improvement effect of Lihu Lake under two typical water replenishment schemes of Changguangxi water intake in the south and Wuli Lake control gate water intake in the west was analyzed. The results show that the average transparency of Lihu Lake can be increased to more than 0.8 m by both schemes. The average transparency of the whole lake increased by 0.5 m in the southern water replenishment scheme，which was better than that in the western water replenishment scheme. Appropriately increasing the outflow of the eastern outlet can improve the effect of water transparency. Water replenishment will lead to the increase of suspended solids concentration in local areas. Under the condition that the total water replenishment flow is fixed，proper regulation of outlet flow distribution can effectively improve the water transparency of Lihu Lake.