In order to solve the problem of deficiency and excess repair maintenance in the process of elevator system, a resource constrained maintenance of elevator system with the highest reliability is studied. Firstly it expounds the model assumption and create the reliabilty as the objection function. A discrete and nonlinear constrained programming model is established. Then, it gives a simulation based PSO to solve the problem, and it includes particle representation, fitness function, update methods and algorithm process. Finally, there is an example to show tthat the model and algorithm can effectively optimize the maintenace decsion scheme and improve the reliability. It can also provides guidance for decision makers.