Co-morbidity between sleep disorders and psychiatric disorders is common. In recent years， increasing researches focus on the role of sleep disorders in the occurrence and development of psychiatric disorders. In order to explore the role of sleep disorders in the etiology of mental disorders，it is required to achieve accurate assessment of sleep disorders. Sleep disorder assessment mostly comes from self-report and polysomnography（ PSG）. Because of its subjectivity or inability to conduct long-term monitoring， its application in clinical research of mental disorders is limited. Wearable devices have shown promise in complementing the assessment of sleep disorders. This review provides an overview of wearable devices for monitoring sleep and their application in mental disorders research to provide clues for the future.