Based on the conditions of Guanjiao tunnel, numerical analysis of air flow field is carried out by the finite element software—CFD in this paper. The results show that when the wind speed is 11m/s, the outlet to the face is less than 50m was better; if the speed is 8m/s ~ 4m/s, the distance is less than 40m better. Under the same conditions, the face wind speed of 40m is larger than of 30m. The faster of the speed, the greater of the attenuation along the way. The best distance from duct to the face is suggested according to different wind speed, which can provide a reference for the construction ventilation of the similar projects in the future.