Atmospheric pressure glow (APG) plasma treatment does not require a vacuum pump that is equipped with a low pressure plasma device. With treatment for organic powder, APG plasma can modify the surface roughness and wettability. In this study, we treated polystyrene films and powder by APG plasma, surveyed the changes of surface morphology, and examined the antifoaming effects of powders. A high exposure time (for this study, 20 min) in He + CF4 plasma, polystyrene powders were introduced onto approximately 55% of fluorine atoms. This powder gave a better result for antifoaming properties.