Glycomacropeptide(GMP) is a polypeptide fragment derived from κ-casein after rennin treatment.At present,the structures of GMP in human beings,cows and goats have been established.The sialic acid structure contained in the polypeptide chain of GMP is very important for the exertion of the biological function.GMP has many biological functions,such as anti-infection,regulating immunity,anti-inflammation,nourishing and maintaining health,and so on.As a new-type bio-functional protein,it will be more and more widely used in the areas of medicine and foodstuff.