Water quality of West Lake has been greatly improved after implementation of lake restoration projects, such as sediment dredging, wetland reconstructing and water freshening supported by Hangzhou Municipal Government since 1998. Based on continuous data analysis of chlorophyll-a concentrations in West Lake from 1998 to 2007, the chlorophyll-a concentrations in main area of West Lake in 2007 decreased by a range from 42.8% to 87.3% compared with those in 1998. The results showed that the restoration projects played a major role in water quality improvement of West Lake.