The invention discloses a power maintenance tool, and particularly relates to an insulator segment replacement device and a replacement method. The insulator segment replacement device comprises a first end portion assembly, a middle clamping assembly, a bearing assembly and a tension assembly. The bearing assembly includes a pulley and a pull rope. The pulley is connected with the middle clampingassembly. One end of the pull rope is connected with the first end portion assembly. The other end of the pull rope bypasses the pulley and is connected with the tension assembly. The tension assembly is capable of pulling the pull rope, so that the middle clamping assembly applies a tension directed towards the first end portion assembly. The insulator segment replacement device adopts the replacement method provided by the invention, so that the segment type multi-sheet replacement of insulator sheets can be realized. Therefore, the maintenance work efficiency is improved.