On the basis of investigating the environmental information of centralized drinking water sources Chongqing City water quality classification, water quality eutrophic state, water quality healthy risk and water pollution of reservoir-based drinking water sources in Chongqing City were evaluated. And the analytical hierarchy process also was used to evaluate water security comprehensively. Finally, the water security status of reservoir-based drinking water sources of Chongqing City was achieved, which can provide a reference for protection and management of drinking water source. The results show that the water quality of reservoir-based drinking water sources is good, the rate of water sources security reaching standard is 97 percent.