The discovery of hypothalamus Hypocretin (Hcrt)/Orexin system and its relationship with narcolepsy is one of the major advances in sleep medicine. Hcrt/Orexin is a significant neurotransmitter in the circadian cycle of arousal. Basic research about Hcrt/Orexin system has been applied in clinical practice and the measurement of Hcrt/Orexin in the cerebrospinal fluid (CSF) is the golden criteria and classification basis for diagnosis of narcolepsy. Breakthrough advance has been made in genetic immunology of hypothalamus Hcrt/Orexin neuronal apoptosis of narcolepsy patients. Medications aimed at Hcrt/Orexin receptors are considered to be a novel target in the treatment of sleep disorders. DOI: 10.3969/j.issn.1672-6731.2017.09.004