Dust explosion experiments aiming at 4 kinds of coal dust were carried out in a 20-liter spherical vessel to explore the mechanism of dust explosion. The lower explosion limit, the maximum explosion pressure and the maximum explosion pressure rising rate were obtained for the coal dust samples. Influences of coal dust concentration, particle diameter and ignition energy on coal dust explosion intensity were analyzed. Results show that the lower explosion limit decreases with the decrease of particle size. For a given concentration, the coal dust with smaller particle size causes higher explosion pressure. Dust concentration has a significant effect on explosion intensity. The maximum explosion pressure and its rising rate increase first and then decrease with the increase of dust concentration. For sample 3, the peak explosion pressure is corresponding to the concentration range from 400 to 1 000 g/m3, and the maximum explosion pressure is 0.54 MPa. To some extent, higher ignition energy causes more sufficient reaction and results in more intensive explosion. Due to the features of coal dust sample components, experimental data indicate that gas phase combustion plays an important role during the explosion process.