During the primary mirror of space optical remotesensor processing, grinding disc and the primary mirror moving back and forth which operation caused the flexible support structure fatigue life issue. Through the establishment of the primary mirror assembly finite element model, fatigue life of components was analyzed by MSC.Fatigue software with stresslife (SN) method, the weak position of support structure was identified. Simulation error analysis was carried out, and factors affecting the simulation results were discussed. It is verified that the processing and design parameters of flexible support structure are rational through comparing the surface accuracy data of the primary mirror surface which collected before and after the thermal vacuum experiment and dynamic components test. The fatigue life simulation can predict the fatigue condition in the process of optical structure processing, and provide a theoretical basis for design and manufacturing.