On the basis of investigation from 1992 to 1993 on water quality, sediment, biology and pollution sources of Qiandao Lake, the status of water environmental quality in Qiandao Lake and total input of pollutants into the lake were comprehensively assessed.The result indicates that the water quality in Qiandao Lake remains well, while the water quality pollution in local region increases with years and trophic status tends to become mesotrophic.50% of non-point pollution load, equivalent to 95% of total input of pollutants into the Iakef were derived from the upper rivers of Anhui Province.A convection diffusion model of water quality was established and the water quality was predicated.Some protection countermeasures of water env-iornmental quality in Qiandao Lake were suggested.