Evaluation of protection through effective monitoring, while using scientific and objective evaluation method, can timely and accurately grasp the operation status of equipment, so as to arrange the maintenance plan, shorten maintenance time and improve the quality of maintenance. In this paper, the shortcomings of the existing evaluation methods of protection are studied and compared. A fuzzy comprehensive state evaluation method of protection with changeable membership degree is proposed. Firstly, the protection status evaluation index system is further improved. A new evaluation index and deterioration degree calculation model are added. Secondly, a variable membership function model based on the variable coefficient, normal distribution and the comment set as the 4 area is proposed and the dynamic correction of membership fuzzy judgment matrix is considered. A new method of dynamic correction of fuzzy matrix is proposed. A variable weight function with variable amplitude and variable weight coefficient is constructed. Finally, the method is used to evaluate the state of the device, and the feasibility and advantage of the method is verified. This work is supported by National High-tech R & D Program of China (863 Program) (No. 2015AA050104).