Abstract: Emulsifiers are widely used additives in food processing industry. As a natural emulsifier, protein has a great market potential therefore attracted more attention. As the most frequently applied protein emulsifiers, caseinate and whey protein have been extensively recognized and used in foods. The mechanism of protein emulsification was discussed. Conditions for proteins displacement adsorption of protein emulsifier mixture were introduced. Theory basis was provided for development of protein emulsifier mixture with these mechanisms.