Combined with the experimental results from the large tunnel of the Chongqing Research Institute, the mechanism of gas and coal dust explosion was studied. Some concepts about gas and coal dust explosion were introduced such as the form condition and influential factors. Gas and coal dust explosion propagation was researched and the lifting process of coal dust was simulated. When an explosion occurred due to great mix-ture of gas and air, the maximum explosion pressure appeared in the neighborhood of the explosion source point. Before it propagated to the tunnel of the deposited coal dust, the maximum explosion pressure appeared to be in declining trend. Part of the energy was lost in the process of raising the deposited coal dust through a shock wave, so the maxi-mum explosion pressure was smallest on the foreside of the deposited coal dust sector. On the deposited coal dust sector, the explosion pressure rapidly increased and dropped off after achieving the largest peak value. Because of coal dust participation in the explo-sion, the flame velocity rose rapidly on the deposited coal dust and achieved a basic sta-ble value; coal dust was ignited to explode by initial laminar flame, and the laminar flame transformed into turbulent flame. The turbulence transformed the flame fold into a funnel shape and the shock wave interacted with the flame, so the combustion rate rose and the pressure wave was further enhanced. The regeneration mechanism between the flame combustion rate and the aerodynamic flowing structure achieved the final critical state for forming the detonation.