Abstract: According to the actual parameter of across vein roadway tunneling in alpine mine, the numerical simulation was set up, and the computation grids were piecemeal-divided. Referring to the tunneling footage and the distance between venting duct and heading face, the diffusion law of blasting fume under different operating modes was simulated by the Fluent fluid analysis software. The simulation results show that the slower the preclusion speed of CO is, the longer the distance between venting duct and heading face, and the ventilation time has a certain functional relationship between the length of across vein roadway and the distance from venting duct to heading face.