The invention belongs to the technical field of on-site maintenance of a nuclear power plant, and particularly relates to an assembling and disassembling tool used for underwater remote-distance anti-loose damage and bolt spiral twisting. The invention aims at providing a portal and reliable underwater remote-distance operation tool which has the bolt anti-loose structure dismantling, bolt dismantling, bolt automatic clamping, and bolt transferring functions at the same time. The tool is characterized by comprising a main body, a positioning screw, an outer sleeve, a dedicated head, an underwater long rod and a first fixed pin; the upper portion of the main body is sleeved with the underwater long rod, and the underwater long rod is fixedly connected with the main body through the first fixed pin; the outer sleeve is arranged on the main body, is in sliding connection with the main body through the positioning screw, and can move in the axial direction relative to the main body; the dedicated head is fixed to the lower end of the main body and is located in the outer sleeve. Due to the process equipment design, the tool is successfully applied to inner component maintaining of FangShan 1# and 2# nuclear power unit QF-OT101 and QF-OT201 nuclear reactors, and the effect is good. The tool serves as the Fang Shan overhauling special project and is the earliest successful implementation and finishing project in the overhauling special project.