Using esterified soybean protein and chitosan as raw materials, according to the mass ratio of esterified soybean protein and chitosan as 1∶0.1, the esterified soybean protein and chitosan solution were mixed and stirred at room temperature for 3 h to prepare esterified soybean protein. The functional properties of esterified soy protein-chitosan complexes were investigated under pH 5.0 conditions. The structure of esterified soybean protein-chitosan complex was studied by infrared spectroscopy and fluorescence spectroscopy, and the effect of esterification modification and chitosan complex modification on the emulsification and antibacterial properties of the complex was discussed. The results show that hydrogen bonds are involved in the formation of esterified soybean protein-chitosan complexes; at pH 5.0, compared with esterified soybean protein, the emulsifying activity of esterified soybean protein isolate-chitosan complex (MSPI-CS), esterified glycinin-chitosan complex (M11S-CS), esterified β-conglycinin-chitosan complex (M7S-CS),were increased to 10.8 m2/g, 9.0 m2/g, 12.0 m2/g, and the emulsion stability were increased to 88.9 min, 71.4 min, and 95.4 min, respectively; The inhibition zone diameters of MSPI-CS, M11S-CS, M7S-CS against Escherichia coli, Staphylococcus aureus and Salmonella all increased; emulsions were prepared with MSPI-CS, M11S-CS, and M7S-CS as emulsifiers, the average particle size of the emulsions decreased to 255.2 nm, 315.6 nm, and 253.6 nm, and the absolute values of Zeta-potentials increased to 22.07 mV, 20.68 mV, and 22.33 mV. At the same time, the storage stability of the emulsion is improved.