Abstract: In order to investigate the characteristics of air-velocity distribution in the air-velocity field of air-assisted sprayer and effect pattern of various factors, so as to discover its working principle, a simulating model of air-velocity distribution on Hardi LB-255 air-assisted sprayer was developed based on CFD technology. The relative errors of simulated results were confirmed through corresponding experiments on the same condition. Based on the model, the air-velocity distribution pattern and spray mechanism were also obtained. The simulated results show that inlet velocity has little effect on the distribution pattern, but the distance to sprayer center and nozzles has a great effect on it. The nozzles caused velocity fluctuation in simulating filed, but it is good at improving spray quality. Meanwhile, the simulated results were compared with the corresponding experimental data. The results of comparison show that the model can accurately predict air-velocity distribution pattern of LB-255 sprayer.