In this paper, WPC-isomalto-oligosaccharide conjugate was prepared by Maillard reaction. Response surface methodology was used to optimize Maillard reaction factors in order to get Maillard reaction products with the highest degree of graft. The results indicated that reaction temperature 90 ℃, weight ratio of WPC to IMO 1:3.125, pH 9.86 and reaction time 78.57 min were the optimum reaction conditions. On these conditions, the highest degree of graft was 25.75%. It was confirmed that the predicted and measured degree of graft values are consistent. At last the glycosylation of WPC was confirmed by SDS-PAGE.