It’s hard to evaluate reliability of guided ammunition test. Put forward the guided ammunition reliability evaluation method, which combining GO method and Bayes evaluation, to solve the problem. Bayes method was used to process the multi-source prior information, Weibull distribution was used as the distribution fitting, GO graph was generated and the operation was carried out by combining with GO method. The system reliability model was established and system reliability evaluation was given. Finally, the effectiveness of the method is verified by taking the guided ammunition control system as an example. The results show that this method not only makes full use of prior information, but also embodies the advantages of GO method for complex system analysis.