Most of the coal mines in China are mined underground, so the ventilation work is very important. It has high requirements for the efficient and stable operation of the main fan to ensure safe production. The basic requirement of mine main fan is efficient operation and steady start-up. In this paper, the principle and mode of speed regulation of mine fan and the start-up characteristics of fan are studied, and the MAF-3000/1700-1G fan of Yangpoyan in Huayang No. 1 Mine is transformed by frequency conversion. The practice after the transformation shows that the high-voltage variable frequency speed regulation device has good starting characteristics and speed regulation performance, which ensures the efficient and stable operation of the mine fan.