Abstract: An active thermal balance method of mine electric traction system was proposed to solve the system heating, which completed on-line self-adjustment of motor stator current amplitude and switching frequency of driving system by returning temperature signal of the electric traction system in real time. An optimized d,q axis current vector calculation method based on the temperature signal was proposed, which could make the electric traction system work at working characteristic curve with the maximum overall efficiency. The method has been verified by using 15 kW permanent magnet synchronous motor speed-adjusting system. The experimental result shows the method can ensure dynamic and stable performance of the mine electric traction system and decrease hotspot safety.