Allyl group-capped polystyrene macromers (PS-allyl)，anicnically synthesized with n-BuLi，were copolymerized，using vanadium compounds as catalysts，with ethylene and pro-pylene to form graft copolymers EPR-g-PS with polystyrene (PS) branches randomly distribu-ted along the E-P copolymer (EPR) backbome．The highest efficiency in macromer incopora-tion was about 70％．Copolymerization parameters affecting mobility of the macromer，such as MW and dosage of the macromer，concentration of catalyst，and reaction temperature，strongly affect copolymerization and structure of the copolymers．The unreacted macromer was successfully separated from the graft copolymer by selective precipitation with MEK．The composition and MW of the purified copolymers were measured by Uv，NMR，osmo-mertry and GPC methods．Characterization results showed that PS-content of the copolymers ranged from 5 to 45％ by weight，MW of PS branches being 1.0一7.8×104 and Mw／Mn of the branches 1.05—1.17．Average number of branches per molecule was 1—4．