The evaluation of the economic life of the protection device can provide important decision basis for the secondary equipment condition maintenance and substation planning, which also can Improve the competitive advantage of enterprises. Based on the theory of life cycle management, a new economic life evaluation model of protection device is proposed. Firstly, the concept of health index is introduced to calculate the actual failure rate of the device. The Weibull distribution function is used to fit the failure rate curve of the device; Secondly, it analyzes the other important factors, including the cost of the installation, the operation and maintenance, the decommissioning, the repair and risks. The life evaluation model is established with the daily average consumption as the criterion. Finally, taking a 110kv substation protection device as a practical example, the optimal exit time is beforehand compared with that given by the factory. Considering the actual operating environment and the fault factors, the prediction result is reasonable, which also can be meaningful to the maintenance strategy of the secondary equipment and the planning of the substation.