The graft copolymerization of mixed grafting monomers vinyl acetate and butyl acrylate onto grafting skeleton of corn starch have been investigated using ammonium persulfate as initiator. Starch based wood adhesive prepared by in emulsion synthesis have green material, superior property, low cost. The effects of various factors on the graft copolymerization were studied such as reaction time, reaction temperature, initiator concentration as well as match of mixed monomers. By single-factor tests, the optimum graft copolymerization conditions with higher grafting efficiency and grafting percent ratio correspond to the reaction time of 3h, the graft polymerization reaction temperature of about 65°C, the initiator concentration of 9.7×10-3mol/L, the mixed grafting monomers concentration of 1.0 mol/L, the volume ratio of vinyl acetate to butyl acrylate of 5:5. The starch graft copolymer after purification was characterized, and its properties were determined. IR spectra of graft copolymers indicated that the carbonyl group characteristic absorption peak existed at 1730～1740cm-1 besides that of starch. The XRD pattern showed there were several dispersion peaks, therefore the graft copolymerization was the concomitant structure of a little crystalline state and amorphous state. TG and DTA curves confirmed the occurrence of graft copolymerization, and showed that the thermal stability of starch copolymer was better than that of pure corn starch. Starch based wood adhesive is white or cream white emulsion paste, excellent emulsive properties and high temperature stability. All properties of starch based wood adhesive can meet the national standard HG/T2727 - 95 of polyvinyl acetate wood adhesive, and the compressive shear strength outdistances the national standard especially.