The invention relates to a tool for replacing the first and last insulator on a tension tower of a power transmission line. The tool at least comprises two strip-shaped connection plates; a plurality of maintenance holes are formed in each strip-shaped connection plate; the two connection plates are fixedly connected with each other through the maintenance holes and by means of bolts so as to a replacement clamping tool, wherein the two connection plates intersect with each other with angles formed therebetween; one of the two connection plates is a transverse connection plate which is transversely arranged and is provided with the maintenance holes with the connection bolts; the maintenance hole at one end of the transverse connection plate is connected with the vertical connection plate with the maintenance holes through the bolt; and the maintenance hole at the other end of the transverse connection plate is connected with a vertical connection plate bar with connection holes through the bolt. The tool has the advantages of simple structure and convenient operation, and can assist in reducing the workload of maintenance personnel replacing the first and last insulator on the tension tower, and improving maintenance efficiency and ensuring the reliability of power supply.