A grounding detection device of grounding knife switch comprises an insulating rod. An end cap is arranged at the lower end of the insulating rod, a grounding wire is arranged in the insulating rod, the lower end of the grounding wire is connected with a grounding clamp while the upper end of the same is connected with a grounding detection device body arranged at the upper end of the insulating rod, a metal contact elastic piece is arranged at the upper end of the grounding detection device body, and a grounding detection circuit is arranged in the grounding detection device body. Connection of the grounding detection device and a grounding network can be realized conveniently through the grounding wire, and a grounding point is provided for the detection device; the grounding detection device can provide acoustic signals and optic signals when grounding is good, operation is convenient, and the grounding detection device can detect whether the grounding knife switch is grounded well or not, so that personal safety of maintenance personnel is ensured.