Abstract: Dicumyl peroxide was used as an initiator in the reaction of grafting PP onto AN in a medium of supercritical carbon dioxide. IR was used to characterize the polymer. When the reaction temperature was 140 ℃,reaction time was 5 h, and AN content was 30 %，the grafting rate was 18.45 %, which was better than solution method.

Key words: supercritical carbon dioxide, polypropylene, acrylonitrile, graft ratio