Abstract: A covalent polymer was formed by the graft reaction of different molecular weight glucans and peanut protein isolates,and their structural characteristics and rheological properties of the formed emulsion were analyzed. The influence of the molecular weight of glucan on the structural and emulsion properties of peanut protein isolate were observed at multiple angles and the reasons were explained. The grafting degree of the grafted product confirmed the occurrence of the grafting reaction,and the grafting degree was lower with the increase of the molecular weight of dextran. The secondary and tertiary structures of the covalent polymers had changed,the α-helical structure reduced in the secondary structure,the β-turn structure increased. The change of PDC2,a covalent polymer formed by the grafting of 20 kDa molecular weight dextran onto peanut protein isolate,was more obvious. In the tertiary structure,PDC2 became looser. The surface hydrophobicity index of PDC2 increased obviously,reached 783±19,indicating that the intermolecular hydrophobic force was greater. In the emulsion system,the intermolecular intermolecular force was obvious,and the resistance shearing force was greater. The force maintained the stability of the emulsion system. Dextran grafting could improve the functional properties of peanut protein isolates. Among them,the improvement of dextran with molecular weight of 20 kDa was the most obvious,which provided a certain basis for broadening the application of peanut protein isolates in the food industry.