Abstract: An air-blast atomizer consisting of a centrifugal nozzle and co-dual-swirl cup was experimentally investigated to obtain atomization characteristics.The radial columnar swirlers were adopted.The experiment was performed in the room temperature and atmospheric pressure to obtain Sauter mean diameter and Rosin-Rammler distribution parameter at different atmosphere pressure drops and fuel pressure.In the experiment,the fuel was RP-3.Sauter mean diameter and distribution parameter of fuel spray were measured by Marlven particle size analyzer in the downstream 50 mm of the nozzle.The experimental results show that Sauter mean diameter decreases and distribution parameter increases with rising atmosphere pressure drops and fuel pressure.Two Sauter mean diameter calculation models were adopted in two different air pressure drops(Δp/p＜3% and Δp/p＞3%).