Abstract: The Gaoersi Tunnel of the No. 318 National Highway is located at the border of Kangding County and Yajiang County, and is an extra-long single-tube bidirectional highway tunnel at high altitude. This tunnel passes through the Tiemengou regional fault zone and F4 buried fault. The stratum and lithology at the Kangding end is mainly Triassic phyllite, and it is entirely Triassic phyllite at the Yangjiang end. The risk assessment for this project is at the primary stage. The risk assessment process with subsections, engineering analogy based checklist for risk identification, and Delphi method were used to evaluate the risks following the requirements of "Guidelines for Highway, Bridge, and Tunnelling Engineering Security Risk Assessment in the Design Stage" and other codes and rules for tunnel risk management both at home and abroad. The potential risks and risk classification and countermeasures for the Gaoersi tunnel are addressed.