Abstract: The GO methodology is a success-oriented method. In this paper, the GO methodology was used for analyzing the failure rate of NPP’s main electrical connection system. The detailed GO chart of typical one and a half breakers system was given. The calculation formula of multi-state system failure rate was deduced and the quantitative analysis was made. Then by comparing the results of GO methodology with that of the FTA method, the correctness and advantage of the GO methodology for the multi-state complex system are verified.