Maintenance philosophies and their activities have always been a major concern in industry. So, every industrial complex needs a clear and comprehensive maintenance plan to keep its equipment reliable and available. In this study, we proposed an AHP model combined with the BOCR method to select the most reliable maintenance strategy for a combined cycle power plant (GTG-HRSG). Five well-known maintenance alternatives including root cause analysis, condition-based maintenance, reliability-centered maintenance, run-to-failure and preventive maintenance are chosen to be evaluated by several experts from various departments of operation, planning and maintenance via three priorities of economic, technical and operation and 30 sub criteria and controls. Then, five different BOCR synthesize methods have been utilized to rank maintenance alternatives. The final result shows that four out of five synthesize methods have ranked RCA as the top maintenance strategy and RCM as second. In one other method, the rank of these two strategies is vice versa.