Human milk oligosaccharides (HMOs) are one kind of the core components that distinguish human milk from animal milk. In recent years， with the rapid advancement in the technology of separation and purification for HMOs. It is realized that HMOs play an important role in the establishment of early intestinal microbiological environment， the development of the intestinal immune system， and the resistance to pathogenic microbial invasion. One of the unique metabolic characteristics of HMOs is that they are not decomposed or absorbed in the upper digestive tract but intactly reach the colon and rectum， where they are decomposed and utilized by the microbial flora. Therefore， clarifying the metabolic process of HMOs in the intestinal microenvironment is crucial for elucidating the material basis， mechanism of action， and structure-activity relationship of their key functions. This article aims to review the latest research progress on the structural characteristics of HMOs and their metabolic patterns in the intestinal microenvironment， providing a theoretical basis for further exploration of the biological activities and pharmaceutical transformation of HMOs.