Abstract: Depression is a mental illness that seriously affects public health, but its etiology and pathogenesis have not been fully elucidated. According to the clinical manifestations, Chinese medicine classifies depression as a constraint syndrome. By sorting out the meaning of constraint, it is found that constraint involves both the etiology and pathogenesis, as well as the disease per se. The pathogenesis and clinical manifestations of depression coincide with those of the constraint syndrome in Chinese medicine. Thus, the clinical diagnosis and treatment can be made by referring to the "constraint syndrome" in Chinese medicine. Considering "fire constraint" is the key pathogenesis of depression changing from mild to severe, the clinical treatment of "fire constraint" should be based on the principle of differentiating the deficiency or excess syndrome. For example, the treatment on the excess syndrome of the fire constraint should be clearing and purifying, while the treatment of the deficiency-excess complex should be unblocking and reinforcing.