Abstract: The safety injection system in nuclear reactor can be regarded as a dynamic system which contains complex operation sequences. The application of GO-FLOW methodology was studied to the reliability analysis on the safety injection system in this paper. A equivalent calculating model of reliability parameter, which can be used to calculate the state probability of the repairable component containing two failure style, was put forwarded, and the validation of the calculating model was also discussed. A practical calculating example was presented, and it shows that the GO-FLOW is an effective tool in reliability analysis of dynamic system containing complex time sequence problem, and its ability in dealing with the multi-state problem is improved by the equivalent calculating model of reliability parameter.