Modern microecology states that there are a lot of commensal bacteria on the surface and inside human body

and most of them reside in the human intestines. The microbiota

which colonize in the gut of the host

the host

and the environment

together constitute a unity of dynamic equilibrium. Intestinal microecology is mainly to explore the structure and function of gut microbiota in the bodies of healthy human beings

to discover the influence of the structural disorder of gut microbiota on human health

and to use its intervention to guide the host to live healthily. Human ’s constitution in TCM theory is considered as an inherent characteristic

which is formed on the basis of the prenatal and postnatal development of human beings

and affects morphology

physiology and psychology. The human gut microbiota are involved in many physiological and pathological activities

and their changes could reflect the physiological and pathological state of the host

so the research method of using intestinal microecology to study TCM constitution could be of important significance in the individual treatment. The four basic principles and three scientific questions of TCM constitutional theory are strongly interrelated with the basic theory of intestinal microecology

and they could serve as mutual interpretation. Based on the study result of modern intestinal microecology

this paper attempts to combine TCM constitutional theory with intestinal microecology

and offers microscopic interpretation of the four basic principles and the three key scientific questions of TCM constitutional theory.