Abstract. The failure rate of it will increase with the increase of the system running time, the traditional periodic preventive maintenance can meet system failure characteristics, so improving the safety of gas pipeline and searching the system elastic maintenance period mode have the important practical significance. To improve the reliability of the system, control maintenance costs, according to the change of system failure rate, this paper will combine system reliability with the efficiency of system maintenance, on the theory of preventive maintenance, and use age reduction factor to establish reliability-maintenance cost multi-objective optimization model of the system. Combining with the engineering example, apply the multi-objective particle swarm optimization algorithm to solve the model example, in MATLAB platform.