As the determination for the cycle of the overhaul depends on experience now, the determi-nation cant meet the safety and economical requirements.Risk analysis technology was used in thedecision making in order to realize the scientific decision.The risk identification technology was usedto find the key parts of operation.Combining with the characteristics of the overhaul, the model ofprobability of failure and the loss cost were proposed.In the end, the decision-making model depen-ding onagementthe least CER was established.The results can be used as the theoretical basis for the man-of cycle decision.