The invention relates to a junction box installation method. The junction box installation method comprises the steps of opening a box cover, and passing a wire through a through hole; removing an insulating shell at the end part of the wire so as to expose a conductive wire at the end part of the wire; installing the exposed conductive wire to a wire clamping slot of a main wiring seat and a wireclamping slot of a subsidiary wiring seat when the wire is installed to a wire joint, keeping a certain distance between the subsidiary wiring seat and the main wiring seat, rotating the subsidiary wiring seat around a cylinder so as to enable the conductive wire to be wound on the cylinder; and finally, installing the box cover to the box body. The connection between wires is faster and more convenient after adopting the joint, and the cost is saved.