Abstract: Casein glycomacropeptide is a sugar chain- containing polypeptide with a plurality of physiological functions, which is generated by hydrolyzing a kappa-casein protein.The hydrolysis process conditions of yak milk casein glycomacropeptide was studied.The optimum enzyme hydrolysis conditions were: substrate concentration of 50g /L, E/S0.5 /100, reaction temperature of 45℃, hydrolysis time for 3.5h. The casein glycomacropeptide product yield was 9.4% and the purity of CGMP was 96.78%.The protein content of the product was 87.18% and the sialic acid content of the product was 6.125mg /g.