The inability to sleep is called insomnia in clinical practice. Insomnia can be divided into two categories according to the etiology: primary and secondary. Primary insomnia usually lacks a clear etiology, or after excluding the etiology that may cause insomnia, insomnia symptoms are still left behind, mainly including three types of psychophysiological insomnia, idiopathic insomnia and subjective insomnia. The diagnosis of primary insomnia lacks specific indicators and is mainly an exclusionary diagnosis. When the possible causes of insomnia are eliminated or cured, but insomnia symptoms remain, primary insomnia can be considered. Psychophysiological insomnia is found to be clinically caused by a certain or long-term event that affects the functional stability of the limbic system of the patient’s brain, and the imbalance of the stability of the limbic system function eventually leads to the disturbance of the sleep function of the brain, and insomnia will occur. Secondary insomnia includes insomnia caused by somatic diseases, mental disorders, substance abuse, and insomnia associated with sleep breathing disorders and respiratory movement disorders. Insomnia often occurs simultaneously with other diseases, and sometimes it is difficult to determine the causal relationship between these diseases and insomnia, so the concept of pathological insomnia is often proposed in recent years to describe those insomnia that is accompanied by other diseases.