Yin deficiency is a symptom of Yin deficiency. Yin deficiency refers to the loss of essence, blood, fluid and other substances in the body, and Yin deficiency cannot cure Yang, resulting in Yang being relatively hyperactive, and the function showing the pathological reflection of deficiency hyperactivity, so there is the saying “Yin deficiency is heat”, which is formed by the cause of over-polarization of fire, injury to Yin or long-term disease that depletes Yin. The treatment should be based on nourishing yin and clearing heat, which can be treated with the Chinese medicine Liu Wei Di Huang Wan, Zhi Bai Di Huang Wan, etc., or with the use of tonics. Yang Ming, Department of Traditional Chinese Medicine, Henan Provincial People’s Hospital