The utility model relates to a single-chip microcomputer controlled positioning device for grounding faults, which belongs to the field of electrician protection and is mainly composed of a micro-current sensor a multi-way switch, an 8098 single-chip microcomputer, a transmitter, a phase-sensitive circuit, an analogue-to-digital converter, a detector, an absolute value circuit, a low frequency voltage sampling circuit, a synchronization signal forming circuit, a DC sampling circuit, a shaping circuit, a low frequency signal source, a function selecting circuit, a display circuit, an alarm circuit, an electric level transfer circuit, etc. The utility model can detect the ground faults and the insulating conditions of each branch circuit of a DC system, can realize the automatic searching of the branch circuits with faults, and can also rapidly detect the specific position of a ground fault.