Abstract: Based on the No.1 tunnel in Daliangshan, taking the excavation length of 100 m as an example, four factors, such as the diameter of air duct, the distance from the outlet end of the air duct to the working face, the position of the air duct and the degree of the air duct sticking to the wall, were selected to carry out the orthogonal test of 4 factors and 3 levels.The numerical model of gas tunnel ventilation was established for analysis, and the optimal setting scheme of the air duct was verified.The results show that the maximum factor affecting the gas concentration on the tunnel face is the diameter of the air duct, followed by the distance between the outlet end of the air duct and the tunnel face, the position of the air duct and the degree of the air duct sticking to the wall.According to the range analysis, the optimal parameters for the placement of the flat duct are 1.5 m in diameter, 5.0 m in distance from the outlet of the duct to the face of the tunnel, 0.2 m in distance from the hanging position to the spandrel and the degree of adherence.The optimal parameters for the main tunnel duct are 1.8 m in diameter, 7.0 m in distance from the outlet of the duct to the face of the tunnel, 0.2 m in distance from the hanging position to the vault and the degree of adherence.Through simulation, it was found that the maximum gas concentration in the flat channel is about 0.1%;The maximum gas concentration in the main tunnel is about 0.2%,all below 0.25%,which meets the regulatory requirements and verifies the feasibility of the design scheme.