Abstract: In this paper, milk was hydrolyzed with trypsin or flavourzyme in single or two-step method to examine the antigenicity change of αs-casein, α-lactalbumin, β-lactoglobulin. Result showed that the antigen reducing rate of αs-casein, α-lactalbumin, β-lactoglobulin were 83%, 91%, 13% respectively after trypsin hydrolysis for 60min. The antigen reducing rate of αs-casein, α-lactalbumin, β-lactoglobulin were 93%, 93%, 55% respectively after flavourzyme hydrolysis for 60min. The antigen reducing rate of αs-casein, α-lactalbumin, β-lactoglobulin were 96%, 96%, 71% respectively after trypsin hydrolysis for 40min and flavourzyme hydrolysis for 20min. Therfore, two-step hydrolysis of trypsin and flavourzyme can significantly reduce the antigenicity of milk protein and bitter.A large number of peptides whose molecular weight below 5000u were produced after double enzymes hydrolysis by step. The technology of milk hydrolyzed by trypsin and flavourzyme in two-step will provide theoretical basis for infant formula milk protein desensitization.