Assembling jig for installing conductive elastic piece and assembling method of assembling jig

The assembly jig comprises an inner sleeve, an outer sleeve and a middle rod, the outer sleeve is provided with a second installation hole of the inner sleeve in a penetrating mode, the outer peripheral wall of the outer end of the inner sleeve is installed in the second installation hole in a clearance fit mode, and the positioning outer peripheral wall of the middle rod is installed in the first installation hole in a clearance fit mode. An annular elastic piece ring groove is defined by the inner circumferential wall of a second mounting hole, the axial end wall of the outer end of the inner sleeve and the positioning outer circumferential wall, then the conductive elastic piece can be preassembled in the elastic piece ring groove in a form-stable mode, the conductive elastic piece is kept in an annular state, then the conductive terminal can be arranged at the outer end of the middle rod in a sleeving mode, and the conductive terminal and the outer sleeve are driven to be pressed downwards, so that the mi