A plasma surface treatment of polymer powders was carried out in a fluidized bed reactor with CF4 glow discharge. The chemical and physical properties of the modified HDPE powders have been determined by ESCA and DSC. With the plasma treatment, HDPE powders are fluorinated into CHF-CH2, CHF-CHF and CF2 groups without change of bulk property. The extent of fluorination increases up to 61% with the treatment time and rf power. The fluorination increase with the composite parameter [(W/FM)t] down to 2,000 GJ.s/kg, thereafter it remains constant.