Abstract: In order to explore the variation characteristics of fire pressure in the shaft during mountain tunnel fire，numerical simulation method (FDS) is used to research the flow characteristics of smoke when the fire source is near the shaft or away from the shaft，and analyze fire pressure's variation law in the shaft under longitudinal ventilation. The results showed that，due to the influence of flue gas vortex，the fire pressure in the shaft shows a non-monotonic tendency，which is different from the traditional slope tunnel fire. Thus the theoretical model of tunnel fire pressure can't be used to predict the fire pressure in the shaft directly. With the longitudinal wind speed from 0 m/s to 3.5 m/s，the fire pressure in the shaft increases gradually，and the maximum difference is about 40 Pa. When the fire source is near the shaft，the fire pressure in the shaft is higher than that is away from the shaft. When there is without longitudinal wind，the maximum difference is about 25 Pa.

Key words: tunnel fire, numerical simulation, shaft, longitudinal ventilation, fire pressure