Abstract: According to reasonable simplifying forces exerted on a droplet, the dynamics equation of a droplet at the swirler area in Swirler Pattern Separator is given. Numerical simulation, which is verified by the conclusions from the experiment, is used to discuss the variable percentage of droplets passing throw the swirler area, droplets impacting the swirlers and the barrel wall in accordance with droplets average diameter, air inlet-velocity and swirler angle. The percentage of droplets impacting swirlers appears to increase when droplets average diameter or air inlet-velocity or swirler angle increases. In addition, swirler angle has little effect on the percentage. The more the rate of drag force to inertial force accumulating in droplets moving time, the more difficult for droplets to impact swirlers.