Emulsion graft copolymerization of methyl methacrylate(MMA) onto gelatin in aqueous solution by potassium persulfate(KPS) with sodium lauryl sulfate(NaLS) as an emulsifier was carried out at the various concentrations of emulsifier, initiator, and monomer. Gelatin conversion, MMA conversion, graft yield, and grafting efficiency of the emulsion graft copolymerzation were higher than those of graft copolymerization in the absence of emulsifier. The graft yield and the amount of hompolymer ware increased because of the acceleration of free radical formation with initiator concentration. The graft yield and grafting efficiency were increased with MMA concentration generally, but at the higher concentration of MMA the grafting efficiency was decreased slowly owing to increase of homopolymer formation.