Based on the characteristics of outdoor installation protection and guided by an efficient and comprehensive inspection, an outdoor installation protection inspection mechanism is proposed which combines factory inspection and field replacement inspection. Firstly, the overall framework of outdoor installation protection is briefly described. On this basis, the overall inspection plan is elaborated. Then the process and content of factory inspection and field replacement inspection are described in detail. Compared with the inspection mechanism of the traditional protection device, the scheme of this paper has obvious advantages in the inspection efficiency and work safety. The plan includes the all functional tests of outdoor installation protection, and incorporates the speciality of outdoor installation protection in operation and maintenance, making the plan more practical. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52199717002A).