To overcome the difficulty of constructing complex electromechanical products' reliability mathematical model, a modeling method which combined function-motion-action(FMA) decomposition withfault tree analysis (FTA) was introduced, reducing the difficulty in constructing the reliability optimization modelThen the hybrid GA-PSO algorithm was put forward for solving the problem of trapping in local optimum easily of genetic algorithm(GA) and weak global search capability of particle swarm optimization (PSO). Through the analysis of grinding machine, it is proved that the optimization model constructed by FMA-FTA is feasible and the optimization result of GA-PSO algorithm is effective.