Abstract: Based on the operating principle of the operating mechanism, secondary circuit design, and the experience of field operation and maintenance, the failure of the three-station GIS isolation switch is analyzed and investigated, and an improved scheme is proposed to replace the original travel switch with contactor node to realize the locking function and replace the slow motor to facilitate the braking.Through the comparison of motor current curve and cycle operation, the effectiveness of the scheme is verified, and the hidden danger of the device′s rejection is eliminated.