The construction of new generation smart substations makes the internal parameters of protection devices can be observed. It makes up the defect of current state assessment that lack of available data and feasibility. The paper does the practical research on state assessment of protection devices based on the monitored dynamic data and static data accumulated by operation and maintenance. Firstly, the paper improves the existing state assessment method which is based on fuzzy comprehensive evaluation method:supplement the important evaluation index to put forward a more complete evaluation index system; put forward a dynamic correction coefficient which can modify the evaluation result indirectly to make up the insufficient of the existing method that is unable to characterize the variation trend. Then, the paper adds an auxiliary decision rules to complete the possible shortcoming of the established evaluation model. Finally, the paper evaluates a device respectively in the case and analyzes the result to verify the feasibility of the established state assessment method.