Abstract: Mammal milk is not only enriched in nutriments, but also contains abundant biological active substances. There are alsolive cells in milk, too. These biological active substances play important roles in metabolism, growth, development, immunization,antimicrobes, etc either of neonates or of young animals. Some biological active substances are closely related with develop-ment, differentiation and protection of mammary gland. The present paper devoted to the introduction of biological active sub-stance in milk, such as hormones, growth factors, enzymes, immunoglobulins, lactoferrin, milk fat globule membrane proteins,bioactive peptides and so on.

Key words: milk, biological active substances, protein, bioactive peptides