Abstract—Dissociative Identity Disorder (DID), which is also known as Multiple Identity Disorder, is characterized by two or more distinct personalities exist within the same person. However, it is very common in reality. In order to have better knowledge about DID, this paper introduce DID from several aspects. The first is some basic facts of DID about how DID happens in reality. Second, symptoms will be mentioned by including DSM-5 diagnostic criteria which is used when diagnosing patients in the medical profession. Finally, the most important research orientation is the causes of DID about childhood experience and influences. As the conclusion, people should learn more about the disease from aspects of current data source, brain function, symptoms, and causes, not just based on the perception of film or media; meanwhile, it is significant to remind people to attach more importance to children development and their mental health.1