Abstract: At present, the state evaluation for relay devices is too simple, subjective and inconvenient. To make the state evaluation of the relay devices more accurately reflect the state of targeted devices and provide more comprehensive information, a comprehensive evaluation system is established for relay protection and a whole-cycle multi-dimension on-line assessment method is proposed based on combined evaluation methods. Considering the operation conditions of protective devices over the recent years and on the basis of the randomness, fuzziness, importance and feasibility of current assessment method, the fuzzy mathematics theory, TOPSIS method and variable weight analysis method are introduced to optimize all aspects of the protection evaluation work with combination of the cloud method to ensure the objectiveness of the evaluation result. The case study has proved the effectiveness of the proposed method.