The surface of polypropylene (

i

PP) is modified with glow discharge plasma of Ar

so that the modified surfaces of

i

PP films are obtained. The studies of scanning electron microscopy (SEM) show the surface etching pattern of

i

PP films. The chemical structures of

i

PP films are confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The wetting properties of modified surfaces of

i

PP films are characterized by contact angle

and the free energy of surfaces is calculated. The free radical of modification surfaces of

i

PP is measured by chemical method. The surfaces of

i

PP are achieved with Ar plasma treatment followed by grafting copolymerization with styrene (St) in St. The grafting polymer of St onto

i

PP is characterized by FTIR. The grafting rate is dependent on plasma exposure time and discharge voltage. The studies show that homopolymerization of St is undergone at the same time during the graftingcopolymerization of St onto

i

PP.