Taking the control plunger of high pressure common rail injector as the research object,the oil film leakage simulation and structural deformation simulation were carried out by using the methods of computational fluid dynamics and thermal-fluid-solid coupling. The optimization design and scheme optimization of the structure of the control plunger were carried out by using the method of unidirectional fluid-solid coupling. The optimization scheme includes machining the annular groove on the side of the plunger and the blind hole in the center of the plunger，and so on. The best combination optimization scheme was selected,which can reduce the maximum deformation of the control plunger by 12.21% and the average oil film thickness by 36.17%. On the CR3000A high pressure common rail fuel supply test bed, the fuel leakage of the control plunger of BOSCH’s CRI2.0 common rail injector was measured under both static and dynamic conditions. The results show that the measured value of the combined optimization scheme is close to the simulation value, and the combined optimization scheme significantly improves the sealing characteristics of the injector，which proves that the combined optimization scheme has good sealing performance under high pressure conditions.