In order to achieve reliable and efficient combat readiness support, the uncertain factors in missile technical preparation process and the causes of equipment maintainability were analyzed, and the stochastic maintenance distribution of uncertain processes was described by statistical inference method based on usage data. The information of maintainability parameters is introduced into the logic calculation process of graphical evaluation and review technique (GERT) random network, and the random maintenance network model of missile technical preparation process is constructed. The GERT analytical method is used to solve the time of the technical preparation process of certain type missile, and the sensitivity of the model is verified by adjusting some maintainability parameters. The simulation results show that the model and algorithm can provide strong data support for missile support tasks.