Abstract: All coal mine electrical and mechanical equipment on-off state requires real-time access to the monitoring system to carry out real-time monitoring through the monitoring sub-station. In view of the existing sensor stops by a single threshold, it is prone to misjudgment in strong magnetic field interference in the environment, detection of current amplification by fixed mode, easy to make the current too small to be detected, the current is too large due to amplification of the signal feature information lost problem. We design an on-off sensor based on the principle of magnetic induction, the sensor has the advantages of strong anti-interference, and can adapt to different working current mine detection equipment. We detail the sensor detection principle, hardware circuit design and adaptive amplification design, by setting the judgment threshold under way to improve the anti-interference ability of sensor. The results show that the use of existing products sold, the sensor can eliminate the false operation bringing instant strong electromagnetic interference, mechanical and electrical equipment and accurate detection of the working current is greater than 0.5 A and no shielded cable on-off state.