Abstract: To analyze the influence of gas and water supply pressure on particle size velocity of gas water spray in underground coal mine, according to the characteristics and properties of the dust hazard types, we successfully designed and carried out atomization characteristic test for gas water atomization nozzle. The experiment uses a new generation of phase doppler interferometer （ＰDＩ）, we analyze the atomization effect of the spray nozzle forming fog field from two aspects of macro and micro characteristics, the nozzle under the different conditions, such as the fog droplets size and velocity distribution in the field, were determined. Through the analysis of the experimental data, it is concluded that the droplet size decreases with the increase of the pressure in the case of constant water pressure; along the axis direction of the fog field, with increase of the distance between the measuring point and the nozzle, the particle size of fog drops is increased, and the axial component velocity and the radial component velocity of the droplet is decreased accordingly.