To understand the propagation of external fires in excavated tunnels, a combustion model was established using fire dynamics software to analyze the propagation of temperature, airflow, and smoke in excavated tunnels under specific wind speeds and fire source powers. The study shows that smoke propagation can be divided into initial combustion and stable combustion phases, significantly influenced by airflow. In the initial phase, smoke mainly spreads longitudinally. As time progresses, smoke rapidly diffuses to both sides of the tunnel under airflow, forming vortex zones where airflow and smoke converge at tunnel ends. This results in local fluid and thermal circulation, creating localized high-temperature areas. In the stable combustion phase, smoke spreads throughout the tunnel, with significant stratification of airflow at the tunnel end. The enthalpy flow of smoke positively correlates with proximity to the heat source, and the enthalpy difference between adjacent cross-sections at equal distances follows consistent patterns. Grid independence verification was conducted to ensure the accuracy of numerical simulation, and the simulation results were validated by comparison with actual mine fire accident data. This research reveals the fire propagation law under the coupling effect of wind speed and fire source power, providing a scientific basis for improving mine safety management and emergency response capabilities, and offering important theoretical guidance for underground personnel evacuation and rescue.