Delusional disorder is a common disorder that is easily understood, but it is also confused with other disorders, leading to a lack of understanding of delusional disorders. Delusion is a distorted belief, pathological reasoning and judgment based on pathology. It is inconsistent with the patient’s level of education, but the patient is convinced of it and cannot be convinced or corrected by personal experience or experience. Delusions are a major manifestation of thought perversion. Delusions can be short-lived or persistent. Delusions that are coherent and compact are called systematic delusions; those that are fragmented, inconsistent, and lacking in logic are called non-systematic delusions. The content of delusions is usually related to personal experience, social and cultural background. Sometimes they clearly reflect real life content. As time progresses, the content of religion, divine power, ghosts, foxes and fairies has significantly decreased and is replaced by the content of modern technology such as wiretaps, lasers and computers. Delusions are sometimes easily confused with some wrong ideas that normal people adhere to, such as prejudice, superstition, misunderstanding, but these latter ideas are mainly due to the method of thinking, level of awareness, the role of the environment and the influence of personal emotions, lack of scientific knowledge and other factors. They can be corrected with the acquisition of knowledge, through education and life experience. The incidence of delusional disorder is about 3 cases per 10,000 people, but many cases remain undiagnosed, so the actual number should be more than that. Women and men appear to have an equal chance of developing the disease, and the age range of onset is very wide. Although the majority of patients are unmarried, some are married prior to the onset of the disease. The personality traits prior to the onset of the disease tend to be withdrawn and disagreeable. The above can give people a better understanding of delusional disorder, and once people are found to have delusional disorder, they should be treated in a timely manner, otherwise it will affect their future development.