The formula of the atmospheric pressure difference caused by the temperature difference in the tunnel and the environment outside the tunnel was established in this paper based on the Clapeyron equation to study the influence of the temperature difference between inside and outside the tunnel on the energy consumption of the ventilation system. Then, a scaled-down model tunnel is established. The air inside the model is heated by electric heating, the temperature and velocity of airflow along the center of the tunnel model are measured in detail, and the atmospheric pressure difference and wind speed in the model tunnel with different slopes are discussed. The results indicate that the tunnel has an obvious natural ventilation effect under specific temperature difference between inside and outside, and it becomes better as the slope increases. The shaft-type natural ventilation can promote the overall tunnel ventilation, and making full use of natural wind can save 15% of the energy consumption of mechanical ventilation.