Abstract: The influence of soybean lecithin on soybean protein (SPI, 7S and 11S) emulsifying system and the related mechanism were studied.Viscosity, particle size distribution, surface hydrophobicity, Zeta potential of emulsion before and after adding lecithin were determined.The results showed that hydrophobic interaction between protein and lecithin changed protein space structure and lead to the hydrophobic amino acids fold, the emulsion of negative Zeta potential was increased.After adding lecithin to emulsion, particle size of emulsion became smaller, viscosity was thinner, hydrophobic interaction of lecithin and 7S globulin was the strongest.The interaction of SPI and phospholipids depended on its components.