Under the effect of load and environmental factors, concrete dam materials appear different degrees of aging and the performance of dam structures degrades during the service period. With regard to this problem, studies on performance degradation mechanism under the coupling effect of multiple factors were summarized in this paper. Since the performance of the in-service dam affected by the environment and load factors is mainly driven by the evolution of material properties, the performance degradation of concrete dam system was studied from the aspect of load and structural resistance, with emphasis on research status and technical challenges of the degradation mechanism of dam structures and materials under multiple factors synergy. Finally, some key scientific problems needed to be urgently solved on the performance of in-service concrete dams are pointed out.