The invention discloses a low-voltage insulation lead wire waterproof apparatus. The apparatus comprises a main installation sleeve whose lower end can pass through a to-be-protected ammeter box penetrating hole, the upper end of the main installation sleeve is annularly provided with a clamping table whose external diameter is greater than the diameter of the to-be-protected ammeter box penetrating hole, the main installation sleeve is internally provided with an installation through hole used for a wire to pass through, the outer surface of the lower segment of the main installation sleeve is provided with an external thread and is provided with a clamping sleeve in a threaded mode, the outer surface of the clamping sleeve is sleeved by a cutting sleeve, the inner surface of the lower end of the clamping sleeve is at least provided with two clamping pawls which can be open and closed so as to enable the wire to pass through and can clamp the penetrating wire, the main installation sleeve is provided with a locking sleeve which can enable the cutting sleeve to slide downwards to enable the clamping pawls to be closed so as to clamp the wire in a threaded mode. The structure is simple, the assembling and the application are convenient, the clamping mode is reliable, a pathway along which water penetrates upwards is cut off by effectively clamping the wire, and the service life of an ammeter box switch is greatly prolonged.