For it is not accurate under the condition of low availability, VARI-METRIC model of inventory optimization for multiechelon multi-indenture repairable spares was built. Firstly, the birth and death process of each component was established by the prediction of demand rate and arrival rate of each spares in each site. Then, a computational method of availability was put forward based on the birth and death process. With the constraints of availability and objective of lowest cost, the optimal inventory distribution result was obtained by marginal algorithm and the simulation model was built to evaluate and adjust the result. In an actual example, the analytic model and the VMETRIC were compared and described in aspects of optimization performance, calculation precision and applicability by simulation verification. Results show that both the analytic model and the VMETRIC have certain scope of applicability and the method combined analytic model and simulation has a stronger applicability. 