Abstract: To study the flow field characteristics of the forced ventilation in plateau spiral tunnels and the influ? ence of the layout parameters of air duct outlet position on the tunnel construction ventilation effect, this paper studies the flow field characteristics near the tunnel face based on the Wolonggou No.1 tunnel project, by using the Fluent software and taking into consideration two kinds of longitudinal gradients, three kinds of air duct diameters and seven kinds of air duct outlet distances and other factors. The results show that if the air duct outlet in forced ventilation is too close or too far away from the working face, it is not conducive to the ventilation efficiency, and the optimal air duct outlet positions for Wolonggou No.1 tunnel are obtained regarding different longitudinal gradients and different duct layout diameters, which are applied to the tunnel practice, and the reliability of the results is verified by field tests.