Abstract: In order to grasp the influence of structural parameters of internal mixing air atomizing nozzles on the atomization characteristics and dust reduction efficiency, so as to obtain economical and reasonable nozzle structure parameters, the self-designed and developed spray dust reduction experimental platform and the orthogonal design method was used to carry out experiment on nozzle atomization characteristics and dust reduction efficiency under the combination of structural parameters. The experimental results shown that, with the diameter of the liquid cap injection hole increased, the nozzle water flow rate increased, while the air flow rate decreased continuously. Nozzle air flow increased with the number of liquid cap injection hole, whereas nozzle water flow was less affected by the number of liquid cap injection hole. When the diameter of the water injection hole gradually increased, the Sauter Mean Diameter (SMD) increased continuously. SMD with the increase of the number of air injection holes shown a change law of first decrease and then increase, and the minimum value was reached when the number of air injection holes was 4, where the atomization effect was the best. When the air cap outlet diameter was 2.0 mm and 2.5 mm, the nozzle droplet size was smaller. With the increase of the diameter of the water injection holes and the number of air injection holes of the liquid cap, the dust reduction efficiency of total dust and respirable dust both first increased and then decreased, and the best effect of the dust reduction was obtained in the diameter of water injection holes of 1.5 mm and the number of air injection holes of 4, respectively. With the diameter of the air cap outlet increased, the dust reduction efficiency of both total dust and respirable dust increased, but the increase of the dust reduction efficiency was smaller when the diameter of the air cap outlet was greater than 2.0 mm. Comprehensively considering the nozzle atomization characteristics and dust reduction efficiency, for the nozzle air cap, the outlet diameter should be 2.0 mm, for the nozzle liquid cap, it was reasonable to use a water injection hole diameter of 1.5 mm and the number of air injection holes to be 4, which can obtain the highest dust reduction efficiency. It is more reasonable to use the nozzles with the combination of above structure parameters for industrial applications, which can obtain smaller droplet size and higher dust reduction efficiency with lower air and water consumption.