Abstract: Ventilation is always a challenge that tunnel technicians have to face in the construction of long-dis? tance tunnels by the drill-blasting method, especially in the hypoxic plateau. The 32.6 km-long Guanjiao tunnel is characterized by its high altitude, long distance, multiple working faces and ventilation difficulties; therefore, a combined separated inclined shaft and vent-pipe ventilation system is put forward for the first time to solve the tunnel′s ventilation problem during construction. After the selection of a fan and the design of the tunnel ventilation system,a numerical simulation and field measurements were carried out to test the ventilation effects and obtain a reasonable distance from the nozzle of the air pipe to the working face and its relationship to the air speed on the working face when the working face is under construction by the combined ventilation scheme. The measurements show that the poisonous gases (CO, SO2) have a lot to do with the construction situation of the working face, and the ventilation effect is good and meets the current requirements of tunnel specifications for general working conditions.