Abstract: According to the common mistaken idea of the smaller the particle size, the better effect of dust suppression, the paper pointed out that the high pressur e spray dust technology should choose reasonable spray parameters based on dust properties. In the case of W3709fully- mechanized coal mining face of Xiaonan Coal Mine, the theoretical calculations and laboratory test methods were used, dust characteristics were analyzed and the best spray particle size range of 50 ~ 70 μm was determined. Nozzles diameter 1 mm and pressure 12 MPa were selected according to the spray particle size and applied in W3709 fully- mechanized coal mining face, and the dust suppression efficiency of the fully- mechanized coal mining face increased by 86% compared with the original dust suppression measures.