Abstract: The traction power supply system of mine trackless trolley has the dual characteristics of coal power supply and subway power supply. A new traction power supply system for mine trackless trolley is designed. The traction power supply system applies a reasonable way of rectification to control the total harmonic amount of rectifier system injecting into the AC grid and reduce the impact on other devices. This power supply system has perfect measures of relay protection and ground protection, which effectively makes up for the lack of traditional power sources and provides a stable and efficient power source. The results showed that this power supply system produced small DC voltage ripple, which met the operation requirements of uphill and long-distance downhill of overloaded trackless trolley. And this power supply system also realized environmental, safe and efficient operation of underground auxiliary transport.