Abstract: The Dagangshan Hydropower Station began to impound in December 2014, and the water level increased from 975 m to 1130 m in November 2015. The right bank slope was subjected to complex geological condition, including diabase dikes, unloading fissures and fractures, which attributed to the local or overall failure of right bank slope in the process of water impoundment. The evolution of micro-fractures of the right bank slope during impoundment was obtained by microseismic monitoring technique. Combining the abundant microseismic monitoring information, the safety factor of the right bank slope during impoundment was calculated by realistic failure process analysis code in three dimensions (RFPA3D). Through considering the effect of progressive microseismic damage, the results showed that the safety factor decreased as the water level increased. The final safety factor was 1.76, which met the requirement of the specification, indicating that the right bank slope was overall stable in the process of water storage.