Abstract The frost front of a cold-region tunnel is important parameter to determine insulation layers. However, the analysis of frost front under ventilation remains changing due to terrible field conditions. In this paper, in order to obtain the distribution law of frost front in a cold-region tunnel under ventilation, the model experiment system with similarity ratio of 1:37 was built relying on the Daban Mountain tunnel. The temperature field of model was analyzed under different airflow temperatures and inlet wind velocities. The radial three-domain governing equations and longitudinal parabolic governing equations of frost front were established. The correctness of the governing equation for frost front was verified in comparison with field data. The modified calculation model of frost front could be used to the approximate estimation for frozen depth of a cold-region tunnel and check the correctness of the numerical solution and computer program.