.This paper uses Fire Dynamics Simulator (FDS) to study the effect of the longitudinal distance from the shaft to the fire source on the natural smoke exhaust of the tunnel fire with one closed portal, and analyzes the temperature distribution of the smoke and the shaft’s smoke exhaust efficiency. The results show that when the shaft is located downstream of the fire source (Ds0), the smoke exhaust efficiency increases slightly with the increase of the distance from the shaft to the fire source, but the overall value is relatively small. When HRR is fixed, the shaft located downstream of the fire source has a higher smoke exhaust efficiency. As the distance between the shaft and the fire source increases, the plug phenomenon decreases.