Abstract: Influence of concentration, particle size and ignition energy of coal dust on secondary explosion characteristic of coal dust were studied by use of 20 L spherical explosion device, and the secondary explosion characteristic of coal dust was compared with the first explosion characteristic of coal dust. The results show that with the increase of coal dust concentration, the maximum pressure and the maximum rising rate of pressure of secondary explosion of coal dust increase firstly and then decrease, the maximum pressure difference between the first explosion and secondary explosion decreases firstly and then increases, and the maximum rising rate difference of pressure between the first explosion and secondary explosion decreases firstly, then increases and decreases lastly; with the decrease of coal dust particle size, the maximum pressure and the maximum rising rate of pressure of secondary explosion of coal dust gradually increase, the maximum pressure difference and the maximum rising rate difference of pressure between the first explosion and secondary explosion increase firstly and then decrease; with the increase of ignition energy, the maximum pressure and the maximum rising rate of pressure of secondary explosion of coal dust, and the maximum pressure difference and the maximum rising rate difference of pressure between the first explosion and secondary explosion increase; the maximum pressure and the maximum rising rate of pressure of secondary explosion of coal dust is smaller than that of the first explosion; coal dust concentration is the main influence factor on the characteristic difference between secondary explosion and the first explosion of coal dust.