The Three Gorges Reservoir has the largest installed power station in the world and generates the most energy in the world as well; the hydraulic turbines employed are the largest Francis turbines. In recent years, total phosphorus (TP) pollution in the reservoir has increased along with eutrophication. TP is the total amount of various phosphides mostly phosphate metal represented by phosphorus element. In this paper, the cavitation pressure characteristics of polluted water were determined through experiments, and the impact on the suction head of turbines during actual operation was studied. Based on the pollution situation, the cavitation performance and the possibility of severe cavitation erosion of turbines in the Three Gorges Reservoir were evaluated. Studies proved that with the increase in the TP concentration, the cavitation inception pressure and critical cavitation pressure increased. This may led to a decrease in the cavitation performance of turbines, which run with polluted water as the working medium. These research results have great importance on cavitation theory and engineering practice.