The invention discloses a high-voltage system, a fault detection device and method of the power switch module of the high-voltage system. The device includes a high-voltage power source end, a low-voltage power source end, a switching assembly, a driving circuit, a current sampling module and a controller; the first end of the switching assembly is connected with the high-voltage power source end;the second end of the switching assembly is connected with the low-voltage power source end; the third end of the switching assembly is connected with the power supply end to the power switch module;the switching assembly is used for controlling the high-voltage power source end or the low-voltage power source end to supply power for the power switch module; the driving circuit is used for driving the power switch module; the current sampling module is used for sampling the current of the power switch module; and the controller is used for controlling the switching assembly and the driving circuit so as to control the low-voltage power source end to supply power to the power switch module, controlling the power switch module to work in a preset detection state and judging whether the power switch module malfunctions according to the current of the power switch module sampled by the current sampling module. According to the fault detection device of the invention, the low-voltage power source end is adopted to perform fault detection on the power switch module, and therefore, the safety of the system can be improved.