Objective To provide scientific basis for prevention of source water pollution and minimization of impacts of biological pollution on drinking water quality.Methods The source water and finished water were determined based on the National Sanitary Method for Determination of Drinking Water(GB5750-1985),the sanitary quality of source water was classified based on the National Standard for Environmental Quality of Surface Water(GHZB1-1999),the sanitary quality of finished water was evaluated based on the National Sanitary Standard for Drinking Water(GB5749-1985).Results 36.8% of the accidents of source water pollution were induced by biological pollution,which mainly occured in rivers and lakes. Conclusion The important countermeasures for the minimization of source water biological pollution were to improve the process of water treatment and to develop the deep water treatment for conventional water treatment.