Elderly type 1 diabetes mellitus is caused by destruction of pancreatic β-cells and is characterized by three more and one fewer symptoms typical of the disease and a high rate of complications. Elderly type 1 diabetes mellitus is the result of a long-term combination of genetic and environmental factors, and viral infections cause associated immune destruction and islet function impairment, which may be the main cause of elderly patients with type 1 diabetes mellitus. Older type 1 diabetes mellitus three more and one less typical symptoms, manifested as more drinking, more urination, more food, weight loss, etc., male patients are significantly more than female, the complication rate is high, the incidence of hypoglycemia is high, hypoglycemia symptoms are not obvious, etc.. Elderly patients diagnosed with type 1 diabetes mellitus should actively cooperate with doctors for treatment; those with suspected clinical symptoms related to type 1 diabetes mellitus are recommended to go to the hospital for consultation.