Failure mechanisms of secondary equipment in intelligent substation are complex, and single indicator does not provide sufficient information to predict potential failures of secondary equipment. Focusing on these problems, a fuzzy comprehensive assessment model of secondary equipment is proposed based on variable weight theory and trapezoidal cloud model. According to the observed internal parameters of devices, a state assessment indicators system of secondary equipment including the intermediate node information in relay protection device is established. The Analytic Hierarchy Process (AHP) and variable weight theory are combined to adjust variable weights of assessment indicators in real time. The eigenvalues of trapezoidal cloud model are used to describe the fuzziness and randomness of the state parameters. The characteristics and variation rule of assessment indicators are associated effectively. Case study shows that the proposed assessment model is feasible and effective, the theoretical basis is provided for condition-based maintenance of secondary equipment and relay protection system in intelligent substation. This work is supported by China Postdoctoral Science Foundation (No. 2017M612909).