Abstract: The roof drainage system is one of the important auxiliary systems of hydropower units. It plays an important role in the safe operation of hydropower plants. Evaluating the health status of the roof drainage system is a necessary measure to ensure the safe operation of the unit. The drainage system is decomposed into multiple levels, combined with data mining to extract the state characteristic indicators that characterize the health state of the system and establish health samples, use the AHP weight method to give weights and build a health assessment model based on the degree of deviation of the health reference value to accomplish the turbine roof drainage system. The health status assessment, combined with the actual operation data of the roof drainage system of the actual hydropower station, verifies the effectiveness and feasibility of the method.