The invention discloses a nut disassembly tool and disassembly method, and belongs to the technical field of mechanical tools. The device comprises a first clamping jaw, a second clamping jaw, a connecting component and a handle, the first clamping jaw and the second clamping jaw are connected on the same side of the connecting component, the first clamping jaw is provided with a first inner sidecorner, an angle of the first inner side corner is as same as that of one outer side corner of a nut to be disassembled, the second clamping jaw is provided with a second inner side corner, an angle of the second inner side corner is as same as that of the other outer side corner of the nut to be disassembled, and the distance between the vertex of the first inner side corner and the vertex of thesecond inner side corner is as same as that between vertexes of outer side corners corresponding to the nut to be disassembled. When the first inner side corner is seamlessly clamped outside of one outer side corner of the nut to be disassembled, the second inner side corner is exactly and seamlessly clamped outside of the other outer side corner of the nut to be disassembled, and the handle is fixedly connected on the other side of the connecting component. The method is implemented based on the device, and the disassembly efficiency of the nut can be improved.