Abstract: This paper analyzes in detail a failure of remote closing of 220 kV substation line switch.The failure process and troubleshooting method are described, and the possible causes of failure are analyzed comprehensively in combination with the electrical principle.Determine the final fault cause according to the troubleshooting.Since the spring mechanism bearing pin, mechanism cam clearance measurement, circuit breaker characteristic test, untouched and secondary circuit are only replaced in this switch.Therefore, in the acceptance at the end of the work, the switch was not remotely opened and closed in the background.In view of this situation, it is proposed that relevant requirements for acceptance should be strengthened, and a reasonable suggestion that a remote opening and closing test should be carried out before the end of the subsequent maintenance work involving the opening and paralleling mechanism.