Aiming at the problems of mutual influence between indexes, unreasonable assignment of subjective and objective weights and fuzziness of membership interval in operation safety evaluation of earth-rockfill dams, an improved combination weighting-cloud model for operation safety evaluation of earth-rock dams was proposed. Taking an earth-rockfill dam in the operation period as an object, the safety evaluation index system of the earth-rockfill dam was constructed. The subjective and objective weights of each evaluation index were calculated by the G1 method and the improved entropy weight method. The game theory was used to solve the optimal weight combination coefficient, and the cloud model theory was introduced to reduce the fuzziness of the membership interval in the evaluation process. The safety state of an earth-rockfill dam was evaluated and compared with those obtained from two traditional combination weighting methods. The results show that the evaluation results of three evaluation methods are similar and consistent with the actual situation. However, the improved combination weighting-cloud model considers the correlation between evaluation indexes, and the use of game theory makes the subjective and objective weight assignment more reasonable, which can more objectively reflect the actual operation state of the earth-rockfill dam.