Abstract: In order to understand the effect of nozzle outlet diameter on dust removal using air-water spray,based on experimental system designed by authors for air-water spray and dust suppression,the spray performance parameters and dust removal efficiency of the nozzle with different outlet diameters were measured. The study results indicate that the water consumption of nozzle appears a linear growth with the increase of outlet diameter,and the air consumption increases in an exponential way. With the increase of outlet diameter,the spray range and droplet volume concentration of air atomizing nozzle increase,but the spray angle increases first and then decreases. It can gain the best quality at-omization with the outlet diameter of 2 mm. Under this outlet diameter of air cap,the sauter mean diameter (SMD) of droplets is smallest,and the particle size presents a normal distribution. The droplet’s velocity falls continuously along the axial line,and it will slow down with the increase of outlet diameter. The droplet’ s velocity firstly increases and then decreases with the increase of outlet diameter. As the nozzle out diameter increases,the total dust suppression effi-ciency and the respirable dust suppression efficiency increase. Taking into consideration of the dust suppression effi-ciency and the nozzle flow,the nozzle with the outlet diameter of 2 -3 mm should be adopted in air-water spray and dust suppression at mine operation site.