The air quality and the toxicity of some harmful gases in plateau area are different from those in plain area. Therefore, the tunneling ventilation in plateau area is more difficult than that in plain area. The correlation between the altitude and the air quality, the calculation of the air volume needed in tunneling ventilation in plateau area, the variation in the ventilation resistance in plateau area and the fan selection in plateau area are analyzed. The study shows that the volumetric expansion and concentration limit of harmful gases at different altitudes should be considered in the calculation of the air volume needed in tunneling ventilation in plateau area and that modification should be made on the fan selection and the ventilation resistance calculation according to the ratio between the air density in plateau area and that in plain area. The paper can provide reference for tunneling in plateau area.