Abstract: As one of the key factors of safe, efficient, energy-saving and environment-friendly operation of the main fan, air volume regulation plays an important role in the safe and economic operation of the coal mine. firstly, the paper analyzes and compares the energy-saving schemes using different methods of regulating air volume control, and puts forward the energy-saving scheme using the variable frequency speed-regulating control technology.secondly, combined with the potential unsafe factors existing in the application of frequency converter in coal mine, a control system of frequency conversion-by-pass power frequency fan based on S7-300 PLC is designed and verified, the verification results show that the fan control system is reliable, ?non-misoperation, non-rejection, and high security. ?Finally, through the actual application case, the paper comprehensively evaluates the application effect of the fan control system, the evaluation result shows that the application effect of the control system is good, centralized control is realized in the dispatch room, and the on-line real-time monitoring of the fan is realized, the goal of reducing the number of people and improving the efficiency was achieved.