In view of the single main protection and main and backup protection system， a protection system reliability model considering the impact of human error is firstly developed in detail， which is based on the condition-based maintenance environment. Corresponding reliability indices are defined， through an example the impact of human error on the protection system reliability is analyzed. The analysis results show that human error has a great impact on both single main protection and main and backup protection system， and human error must be reduced as possible during normal operation and maintenance process. The human reliability and protection system reliability must be improved. Not only reliability of main protection should be increased， but also reliability of backup protection in the multiple protection system，and preventing malfunction of protection system should be guideline.