A missile life span prediction method was researched based on the reliability data of missiles in storage condition. The scientific and practical missile storage life span was provided. According to periodic inspection of missile in storage situation, use the principle of minimum “residual quadratic sum(R2)”, the failure rate of missiles on the service period and the calculation method for the upper and lower confidence interval of the failure rate are put forward as well as the optimal fitting function model. The missile’s storage reliability and its confidence interval were also obtained when the missile was put in the circumstance of air-conditioned storehouse, ordinary temperature storehouse and open air. According to the standard that failure-free rate should be higher than 0.7, the life span of missiles was analyzed based on the periodical check-data of a certain type of missiles and the results were conformed to the reality. The prediction method was proved practical and provided reference of reliability analysis for missile prolongs life.