Abstract: In order to clarify the cause of the failure of the high-voltage cable metal sheath voltage monitoring device, the insulation test of the same type of monitoring device was carried out to obtain the overvoltage withstand characteristics of the device; an electromagnetic transient simulation model of the 220 kV cable line and substation equipment on both sides was established to detect single-phase ground faults during the process, the induced voltage of the cable metal sheath was numerically simulated and the distribution rules of its transient overvoltage and power frequency overvoltage were obtained. And the relevant requirements for the insulation withstand level of the voltage monitoring device of the metal sheath of high-voltage cables are proposed to withstand the overvoltage induced by the sheath under a ground fault.