At present, dust is not only the main occupational hazard factor in tunnel construction, which seriously threats the safety of production and the health of construction workers, but also an important source of environmental pollution. Taking the working face of a construction tunnel as the research object, the numerical model is constructed with the help of fluid software FLUENT, and the dust distribution law of the construction tunnel is simulated and analyzed, so as to provide research direction for environmental protection and personal health protection. The comparative analysis results of numerical simulation and field measured dust concentration show that the dust in the tunnel construction is easy to accumulate in the lower right side of the tunnel. When the fan mouth is 5 meters away from the working face, the dust concentration within 8 meters near the working face is the lowest. When the fan mouth is 10 meters away from the working face, the dust diffusion range is the longest and it is not easy to accumulate.