In this paper a combined approach is presented known as SIWPSO; the main idea of this approach is to get the optimal allocation of cloud service resources to improve the overall outcome of cloud manufacturing. Based on the characteristics of manufacturing enterprises in cloud manufacturing environment, the mathematic model was formulated for resources scheduling and assignment problem in cloud manufacturing. The particle swarm optimization with stochastic inertia weight strategy (SIWPSO) was adopted for the proposed model. Its efficiency is compared with other three particle swarm optimization algorithms. Simulation results show its effectiveness and superiority to solve cloud service resources scheduling and assignment problem.