In order to solve the problem that it is difficult to evaluate the equipment operational availability in development phase, an integrative evaluating method that combines experiment design, simulation modeling and regression tree is proposed. The simulation model of single equipment operational availability under two-echelon maintenance support structure is developed by using arena software, the design of input scenario is accomplished by adopting latin hypercube sampling (LHS), the output data of operational availability is obtained through running the established simulation model, and factors that have obvious influence on operational availability are determined by the regression tree. Finally the feasibility of the proposed method is shown by numerical examples.