Abstract : This paper introduces the ventilation requirements in tunnel construction and the application of variable frequency speed control in fans. A new control system for tunnel construction ventilation based on fuzzy control is proposed, using CO concentration and methane concentration as system inputs and the input voltage of the frequency converter as the output of the fuzzy controller. Simulation results show that this fuzzy control system not only improves the control performance and automation level of tunnel construction ventilation but also achieves significant energy savings. Keywords : Fuzzy control; Frequency converter; Tunnel construction; Simulation 1 Introduction Ventilation is an indispensable part of tunnel construction. During tunnel construction, various harmful gases such as CO, CH4, and dust are generated. Therefore, it is essential to continuously supply outside air to all working faces inside the tunnel to ensure normal breathing for personnel, dilute and remove harmful gases and dust, and maintain air quality in the tunnel. In traditional tunnel construction ventilation in China, there are many methods for adjusting fans, such as fan throttling, blade adjustment, and motor step-change adjustment. However, these methods are difficult to implement in real-time control of the working environment, and energy cannot be fully utilized. This paper proposes a scheme that uses variable frequency speed control and fuzzy control technology to control the input frequency of an AC asynchronous motor, thereby controlling the fan speed. [b]2 Variable Frequency Speed ​​Regulation of Fans 2.1 Variable Speed ​​Adjustment[/b] According to aerodynamic theory, the most reasonable way to change the performance of a fan is to change its speed. This is because when a fan operates in a pipe network where the resistance is directly proportional to the square of the flow rate, although the speed decreases, the fan efficiency remains unchanged, while the fan power decreases significantly due to the reduction in flow rate and pressure. [b][align=center]For more details, please click: Fuzzy Control Technology for Ventilation Systems in Tunnel Construction[/align][/b]