To investigate the influence of altitude on smoke propagation of train fire accident in tunnels，based on the validated numerical simulation method， the sliding grid technology was used to achieve the entire motion process of a train running at a uniform speed in a tunnel， decelerating after a fire accident and eventually stopping in the tunnel. The three-dimensional unsteady N-S equation and RNG k- ε turbulence model were adopted， and the reliability of the numerical simulation method was verified by the datas of the scaled train fire accident test in tunnel. The results indicate that the altitude has a significant impact on the smoke propagation after fired trains stop in the tunnel. Compared with low altitude tunnels at a time， the smoke propagation velocity at the same location as the tunnel vault is faster in high altitude tunnels， and the time when the smoke countercurrents to 50 m upstream of the fire source is earlier. The temperature distribution around the train also shows a rising trend with the increasing altitudes. Compared with the train fire accident in the tunnel at an altitude of 0 m， the time is 102 seconds earlier when the smoke in the tunnel at an altitude of 5 000 m countercurrents to 50 m upstream of the fire source. At the same time， the peak value of temperature at the tunnel vault is increased by 216 K， with an increase of 42.9% when the fired train stopped for 360 seconds.