There is a line under the navel called the abdominal line, abdominal line is a normal physiological situation, regardless of the male and female navel below there will be a clear line, some people pigmentation is very obvious, and some people have relatively fair skin, not easy to form melanin pigmentation, so this abdominal line is relatively inconspicuous, and can not be seen clearly, this is a normal physiological manifestations, there is no need to worry about, abdominal line is regardless of the male and female exist a physiological line, this line for determining the clinical anatomical location of some diseases, certain reference role and reference value. The abdominal line is a physiological line that exists in both males and females, and this line has a certain reference role and reference value for determining the anatomical location of some clinical diseases. Usually in skin diseases, such as melanosis or endocrine metabolic diseases, such as Cushing’s syndrome, Schieffer’s syndrome, the abdominal line will be abnormally obvious, the color will become darker, and the color will be aggravated. However, in diseases with thinning hair, such as vitamin deficiencies or a lack of certain trace elements in the body, or in people with excessively fair skin that is not prone to melanization, the ventral line under the abdomen will be very light and shallow.