The main types and pollution sources of drinking water sources site reservoirs in Cangnan were summarized.The methods of monitoring and evaluating the water quality were introduced.On the basis of monitoring data of the drinking water quality from six source sites reservoirs in Cangnan in recent three years,the water quality in reservoirs were evaluated comprehensively.The results showed that the water quality of Shibakong reservoir progressively deteriorated,while that of the other five reservoirs were basically stable to meet the functional requirements of gradeⅡ water.According to the main pollution sources in reservoirs,the control measures of water pollution were put forward.