Abstract: To address the ventilation challenge in the No.24 main tunnel of the Huangwu Tunnel on the Hanjiang-to-Weihe River Water Diversion Project, where the maximum air supply distance reaches 4960 m, the CFD method was adopted to simulate the flow field of forced ventilation at different construction stages. Based on the RNG k-ε turbulence model, three-dimensional geometric models were established for two stages: the early stage with dual-fan parallel air supply and the late stage with booster fan pressurization. The jet flow at the duct outlet, the air velocity near the tunnel face, and the overall flow field in the tunnel were analyzed. The results show that in the early stage, the air velocity at the duct outlet is about 2.2 m/s, and that near the tunnel face is about 0.5 m/s, with a stable flow field and no backflow. In the late stage with booster fans, the jet velocity at the air inlet increases to about 8.2 m/s, and the average velocity over the whole tunnel section reaches 6.9 m/s, with only slight local vortexes. The air velocities near the tunnel face in both stages are higher than the code requirement of 0.15 m/s, which verifies the rationality of the design and can provide reference for similar projects.