Meiliang Lake is located at north of Tai lake, it is one of the most important part of Tai Lake. Water quality of Meiliang Lake is being worse because the TP, TN and COD is released from the bottom sediment. So th goverment is decided to dredg the bottom sediment to improve the water quality. This paper used WASP5 numerical model to simulate the water quality of Meiliang Lake before and after the sediment dredging. The results show that sediment dredging is useful for improving the water quality of Meiliang Lake.