Milk protein is an important animal protein source for human, and mammary gland is the major organ for milk protein synthesis. However, some free amino acids took up by mammary gland of lactating ruminants are less than their output in the milk. Animals have special needs for proteins or small peptides. Because of their advantageous transmembrane transport system and special physiological function, small peptide nutrition is greatly concerned. Uptake and utilization of small peptides in mammary gland of lactating ruminants and influence factors are briefly reviewed in this paper.［Chinese Journal of Animal Nutrition，2011，23（3）：376-380］