The graft copolymerization of methyl methacrylateand styrene onto natural rubber in the emulsion processwas studied. The graft copolymerization was carried outby varying concentration of methyl methacrylate andstyrene monomers, emulsifier concentration, initiatorconcentration, and reaction temperature. The graftingefficiency, graft ratio and degree of monomersconversion were reported. The molecular weights of freeS/MMA and the frequency of graft chain on backbonerubber were determined by the gel permeationchromatography (GPC) technique. The copolymercomposition was determined by Nuclear magneticresonance spectroscopy (NMR), and Elemental analyzer.The optimum conditions of graft copolymerization were100 parts by weight of monomer per 100 parts by weightof natural rubber latex, the emulsifier concentrationof 1.5 parts by weight, the initiator concentration of1.5 parts by weight, and temperature of 70 degree C for8 hours. The grafted natural rubber product could be usedas an impact modifier for PVC was studied The graftednatural rubber product (5, 10, 15, and 20 phr) and PVCblend were prepared. The effect of grafted naturalrubber product and PVC ratio on tensile properties,Izod impact strength, and hardness were investigated.The tensile strength and hardness decreased withincreasing the grafted natural rubber product, but theelongation at break and impact strength increased withincreasing the grafted natural rubber. The appropriategrafted natural rubber product used were 10 and 15 phr.