Diffuser is a key component of aero-engine compressor， which has an important impact on its performance， efficiency and operating conditions. In order to solve the problem of poor rigidity and easy deformation of insulating sleeve structure in the process of electrochemical trepanning， the optimization method of insulating sleeve rigidity is proposed， strengthening rib is designed at the free end of insulating sleeve， and the fluid structure coupling simulation comparative study under different strengthening rib shapes and sizes is carried out. When the two ends of strengthening rib are round， the width b = 2 mm and the distance from the bottom h = 6 mm， the maximum deformation is reduced by 88.3% compared with the structure without strengthening rib. The experimental research of electrolytic machining is carried out. The stable machining with cathode feed rate of 1.4 mm/min is realized， and the machining stability and efficiency are significantly improved. The effectiveness of the rigidity optimization method of insulating sleeve is verified.