Abstract： Objective To investigate the pathological changes of main organs of patients with diabetes millitus. Methods We analysed 36 cases of autopsy materials with diabetes mellitus retrospectively. Results The main pathological changes are found in pancreases islets and kidney. The morphological changes included decrease of the number,atrophy,hyaline degeneration and fibrosis of islets. The number of B cells in islets and the granules in B cells was decrease. Hydropic degeneration can be seen easily in B cells. Pathological changes in kidneys were nodular glomerulosclerosis and diffuse glomerulosclerosis. In accompanying diseases, 9 cases (25%) are malignant tumors. Analysing of the causes of death,the common reasons were malignant tumors,acute myocardial infarction,hyperglycemic coma, infectious shock, cerebral edema, cerebral hernia, acute necrotic pancreatitis and uremia. Conclusion In the treatment of diabetes mellitus, doctors should not only control blood glucose, blood pressure, keep standard weight, prevent and care infection,but also monitor the onset of malignant tumors closely.