The spare parts inventory and department repair capacity are important factors to influence the process of maintenance turnover for spare part, and it restricts the use effect of equipment. Aiming at the support project evaluation and optimization when the demand of spare parts is dynamic in the mission phases and considering the influence of repair capacity to spare parts repair process, an evaluation model of time-varying availability was set up for the multi-echelon support system with finite repair capacity on the basis of the METRIC methodology and dynamic queuing theory. Based on the evaluation model, an optimization model for the support project of multi-echelon support system during the mission phases was proposed by taking the support cost as the optimization objective and the equipment availability as the constraints. The minimum availability of the whole mission was taken as observation value and the margin optimization was used to get the optimized project for each resource. The analysis results of an example show the availability value for different mission phases can be given by the evaluation model, and the optimized project of resources for the multi-echelon support system can be obtained by the optimization model and method. The proposed models and optimization method can provide decision support to equipment support staff for rational support project.