Infancy is a crucial stage in the human life cycle，characterized by unique constitutions.The gut microbiota，often referred to as the “second genome of the human body”，is a huge micro-ecosystem.The relationship between infant constitution and gut microbiota is closely examined through four fundamental principles in traditional Chinese medicine(TCM) constitution theory.From life process theory，the developmental phases and characteristics of infant constitution align with the colonization and growth of gut microbiota.From genetic endowment theory，genetic factors from parents and prenatal nourishment significantly influence the formation of infant constitution and the structure of gut microbiota.From environmental constrain theory，factors such as living environment，diet，feeding methods，and medication use exert a secondary influence on changes in infant constitution and gut microbiota composition.From body-spirit composition theory，different constitutional types exhibit distinct psychological traits; emotional factors can have lasting effects on both infant constitution and gut microbiota throughout life.Additionally，gut microbiota significantly impacts the formation of infant constitution by participating in early neurodevelopment.