Abstract: The extra-long Que′ershan road tunnel on the No. 317 national road has the characteristics of high alti? tude and geostress, low temperature, low atmospheric pressure and oxygen, and the working environment inside the tunnel is harsh due to low efficiency of ventilation at the initial stage of construction and the emitted hazardous gas from internal combustion engines, affecting health of the constructers and threatening the personal safety. A study on the construction ventilation, oxygen generating and supplying and the techniques for reducing hazardous gas emission from internal combustion engine is conducted. Finally the key techniques for improving the working environment of extra-long road tunnels in high altitude area are proposed.