Abstract: According to the similarity principle, with the ventilation system in mining area of an actual coalmine as prototype, the "simulation experiment system of mine tunnel fire" was established.The physical model of experimental tunnel was built by using GAMBIT software and the body was meshed by using the method of Hex/Wedge-Cooper.The initial and boundary conditions were set and processed.The tunnel fire source was simplified as a steady heat source of fixed volume.The variation law and distribution of temperature field, velocity field, density field and pressure field of smoke flow in fire tunnel were simulated and analyzed respectively with different initial velocity of tunnel entrance.The results show that:after the fire, the smoke flow diffusion range increases, the temperature gradually increases and it is the highest near the fire area; the smoke flow velocity decreases gradually from the inlet to outlet in tunnel, and it greatly reduces at the tunnel intersection due to the presence of local resistance and throttling effect; otherwise, the smoke flow density increases gradually from the inlet to outlet in tunnel, and it becomes greater in tunnel with bad ventilation; the smoke flow density at the top of tunnel is less than at the bottom of tunnel, and the smoke flow pressure is higher overall, but it is the lowest at the outlet of tunnel.