The stability of Glycyrrhiza polysaccharide / casein complex was analyzed by Zeta potential and turbidity， and the structural properties and interaction mechanism of GP/CS complex were investigated by fluorescence spectrum， infrared spectrum and circular dichroism spectrum， ect. The emulsifying stability of compound emulsion was also discussed. The results showed that GP/CS could form a stable complex. When pH=7， the Zeta potential values of GP/CS complexes were between CS and GP solution， with the average particle size increasing and fluorescence intensity decreasing， and the ultraviolet absorption intensity decreasing with blue shift， the intensity and peak width of the absorption peak of the infrared spectrum were changed， and the secondary structure of casein were changed. The electrostatic interaction， hydrogen bonding and hydrophobicity were involved in the formation of the composites. In addition， GP/CS complex could improve the stability of the emulsion. This study provides reference for the application of protein-polysaccharide complex in food field.