Constitution is formed before birth and can be improved after birth. It is stable and also changeable. Theoretically, constitution is the manifestation of the functional state of the internal organs, demonstrating the condition of qi, blood, yin and yang in the body. The body resistance in fighting against pathogenic factors is the specific manifestation of constitution in pathogenesis. Temperament, a concept related to constitution, is a special response of constitution in psychology. Different constitution pairs with different temperament and vice versa.