The invention relates to an insulator string live replacement technique, in particular to a 220kV line L-LF type insulator string ground potential live replacement method. A front clamp of a tool comprises a left clamp and a right clamp, the left clamp is open forked and comprises an outer fork clamp and an inner fork clamp, and the inner fork clamp and the outer fork clamp are structurally matched with a side stepped space of an LF type connecting plate and can be exactly clamped in the side stepped space in a sleeved manner to obtain enough fixed points and connection points in the stepped structure of the connecting plate. Firstly, the front clamp is mounted on the LF type connecting plate by the aid of an insulating operation rod on a cross arm; secondly, a rear clamp is mounted and connected onto an operation screw rod; finally, an insulating pull rod is connected with the front clamp, an insulator string is lifted, and replacement is finished. The method has the advantages that complexity of equal potential mounting operation performed by operators entering an electric field is avoided, the tool is simple and convenient to operate, low in workload and high in operation efficiency, the equipment defect eliminating capacity of live operation is improved, line outage time is shortened, and reliability of grid operation is improved.