Abstract: In order to reveal the mechanism of the medium flow and viscosity in the atomization process of pressure nozzle, a simulation approach combining large eddy simulation（LES） and volume of fluid（VOF） was adopted to explore the flow in the nozzle, and the effects of inflow Reynolds number（Re） on flow coefficient, atomization angle and particle size were analyzed. Results show that the flow coefficient of the nozzle and the liquid film thickness at the nozzle outlet decrease with the increase of Re. When Re is high, the effect of inflow Re on the flow coefficient is less.With the increase of Re, the atomization angle of the nozzle increases. When Re is less than 1 000, the increase of atomization angle is more obvious with the increase of Re. For a certain Re, the atomization angle is almost equal. When Re is higher, the Sauter mean diameters(d_SMD) of atomized droplets are more uniform, and the distribution of the atomization particle size is closer to the characteristics of Rosin-Rammler（R-R） function.