Abstract: In this paper the characteristic of random time dependent structure is studied, and the decline formula of stochastic process strenth is proposed. In the effect of dynamic load the dynamic response of stochastic coefficient structure is analyzed by vibration mould decomposed. The dynamic response spectrum and statistic formula are obtained. The time dependent boundary function is determined. Under some basic assumptions, the reliability formula of time dependent structure is gained. Also the reliability analysis method of servicing structure, and the evaluation formula both in designing period and estimating period are given.