Malondialdehyde was selected as a representative of reactive aldehydes produced in the process of polyunsaturated fatty acids lipid peroxidation catalyzed by lipoxygenase， and the aim of this work was to investigate the effect of malondialdehyde oxidation on the emulsifying properties of walnut protein isolates. The results indicated that as concentration of malondialdehyde increased from 0 to 10 mmol/L， carbonyl content of walnut protein isolates increased from 3.12 nmol/mg to 20.61 nmol/mg； Surface hydrophobicity（H0） showed the trend of first increase and then decrease （P<0.05）； Intrinsic fluorescence of emulsion decreased from 419.97 to 109.86 and maximum emission wavelength moved in the short wave direction； Droplet size distributions and creaming rate firstly decreased then increased； Zeta potential and emulsion stability of the test emulsions firstly increased then decreased； but emulsifying activity decreased form 46.57 m2/g to 26.26 m2/g. When malondialdehyde concentration was 0.1 mmol/L， droplet size distributions and creaming rate reached the minimum value； and zeta potential and emulsion stability reached the maximum value. The analysis of the results showed lower level oxidation could generate emulsion stability of walnut protein isolates， while higher level oxidation had a negative effect on the emulsifying properties.