The graft copolymerizations of acrylonitrile (AN) and methyl methacrylate (MMA) onto chloroprene rubber (CR) were carried out with benzoyl peroxide(BPO) as an initiator. The effect of solvent, mole ratio of AN to MMA, reaction time and temperature, and initiator concentration on graft copolymerization were examined. It was observed that the grafting efficiency increased as increasing mole ratio of AN to MMA. the graft copolymer, acrylonitrile- CR-methyl methacrylate (ACM), was identified by infrared spectroscopy and morphology. Thermal stability of ACM was found to be improved when compared with those of CR.