Abstract: In view of problem that stray currents generate serious threat to safety production of coal mine, the paper proposed detection system of stray currents in coal mine based on magnetoresistance effects. It introduced detection principle of the system, designed detection circuit and sensor peripheral circuit, and completed experiment. The experimental result shows that the system can measure stray current accurately and stably, current detection accuracy basically meets detection requirements and the non-contact method is safe and reliable. The proposed system has great practical significance for mine stray current control.