Abstract: In order to satisfy long-distance transmission requirements of sensor used on underground super long working face, a mine-used intrinsically safe remote relay power supply was designed. Parallel connecting a mine-used intrinsically safe remote relay power supply between the sensor and intrinsically safe power supply can compensate differential pressure on power supply cable of single 24 V power supply, and extend power supply distance. The test results show that the relay power supply can make power supply distance of 24 V intrinsically safe power supply extend at least 2 km, and has small start current, stable output voltage and high performance to price ratio.