Analysis of the failure characteristics of relay protection devices is of great significance for improving the pertinence, effectiveness and economy of maintenance. First, the basic characteristics of relay protection device failure were analyzed, the basic definitions of protection failure and failure rate were explained, and common calculation methods of failure rate distribution function were analyzed. Then, considering the accidental failure and aging failure conditions, based on the Weber distribution method, the relevant parameters of the relay protection device failure function were fitted and calculated using the least square method. The failure rate calculation function of the relay protection device which accords with the actual situation was solved. Finally, the failure rates under different failure modes and different failure assumptions were calculated. The results show that the accuracy of the three-parameter Weber distribution for the failure characteristics of relay protection devices is better than other distribution functions, which fully proves the superiority and rationality of the method.