Abstract: To investigate the influence of the bifurcation angle on the diffusion of blasting gas in T-shaped tunnels built by the drilling and blasting method, this study, on the basis of the bifurcation structure formed by the left main tunnel and 38# cross tunnel in the Yuelongmen Tunnel on the Chengdu-Lanzhou Railway, establishes the 3D mesh models with bifurcation angles of 45°, 60°, 75° and 90° respectively, carries out numerical simulations of the tunnel ventilation by using Fluent and, taking into account the local loss theory, investigates the pattern of wind energy loss at the bifurcation. The results show that in the process of ventilating for the construction of T-shaped bifurcated tunnels, a large ventilation blind zone appears near the side of the obtuse angle of the cross tunnel and the downstream side of the main tunnel without bifurcation, and the range of the blind zone expands with the increase of the bifurcation angle. Comparing the time required to discharge the blasting gas under each construction condition, it is found that the larger the bifurcation angle of the tunnel is, the worse the ventilation effect will be, and the longer the required time will be for ventilation. Through the deduction of the relationship equation between the local loss coefficient and the bifurcation angle, it is also found that the local loss coefficient of the main tunnel is almost independent of the bifurcation angle, while the local loss coefficient of the cross tunnel is positively correlated to the bifurcation angle of the tunnel.