The quantitative impact of land use/cover (LULC) on the receiving water quality is one of research highlights of lake ecology. By using Landsat Thematic Mapper (TM) images and water quality indices (TN, TP, Chl. a, Secchi depth) of four seasons, this paper analyzed the relationship between land use/cover and water quality of Gonghu Bay based on five different buffer zones and the whole bay scale. Results showed that the land use pattern in Gonghu Bay had a significant impact on surface water quality. Construction land and cultivated land had a significant positive effect on water quality in Gonghu Bay, while forest land exhibited significant negative effect on water quality; grass land and non-used land had not significant effect. There was a scale effect between land use pattern and water quality indices in Gonghu Bay. The land use/cover type near to Gonghu Bay had more significant influence on water quality than that away from Gonghu Bay. Studies have shown that the forest land in Gonghu Bay had a strong effect on reducing water and sand, positively improving the receiving water quality. Developing afforestation, returning farmland to forest, and implementing wetland restoration project along the littoral zones within 0-2 km of Gonghu Bay will positively prevent soil erosion and protect the ecological environment.