With the development of the fully mechanized coal mining face in the depth direction, the power supply distance has become longer, and higher requirements have been placed on the power supply system. The selection of the power supply method of the fully mechanized mining face in Shennong Mine was introduced in detail from the determination of the capacity and model of the transformer, the selection of the high-voltage cable of the mobile substation and the power supply cables of various electromechanical equipment, and the selection of the low-voltage combination switch. The design scheme of long-distance power supply system was expounded.