Emulsion graft copolymerization of methyl methacrylate (MMA) onto gelatin in aqeous solution by potassium persulfate (KPS) with sodium lauryl sulfate (NaLS) as an emulsifier was carried out under different conditions such as variations in gelatin concentration, reaction time, and reaction temperature. The grafting efficiency was gradually increased with gelatin concentration, however, the graft yield was increased and then decreased around a certain fixed concentration. The grafted poly(methyl methacrylate) (g-PMMA) was produced rapidly in the early stage but the grafting efficiency was decreased in about 4 hours as the copolymerization was nearly completed. The gelatin conversion, the MMA conversion, and the graft yield were increased markedly, but the grafting efficiency slightyl, with the temperature.