Aimed at some uncertain problems in determining the maintenance period, the maintenance period decision models of missile equipment are established based on RCM. Respectively with the total costs minimum and availability maximum goals established the model, solved the models by Monte Carlo simulation, used fuzzy decision method to determine the optimal preventive maintenance cycle of multi-objective, and the effectiveness of the method is verified with certain missile equipment sealing ring as an example. Practical analysis of results showed that this method is a weighted combination of the costs and availability factors, and it can solve the problem that the low availability and high maintenance costs better. The method has some certain application and reference value.