Diabetes mellitus in children can be detected by fasting blood glucose, 2-hour postprandial blood glucose, glycated hemoglobin, etc. In addition, it is also necessary to combine with the clinical manifestations to diagnose diabetes mellitus comprehensively. The diagnostic criteria for diabetes mellitus in children are the same as those for adults, i.e., typical symptoms of “three more and one less” (excessive drinking, excessive urination, excessive eating, and weight loss) plus venous plasma glucose ≥11.1 mmol/L, fasting blood glucose ≥7.0 mmol/L, or 2-hour blood glucose ≥11.1 mmol/L after glucose tolerance test, taken at any time of the day. mmol/L. The China Type 2 Diabetes 2020 Prevention and Control Guidelines include glycosylated hemoglobin in the diagnostic criteria, and glycosylated hemoglobin ≥6.5% can be used as an additional diagnostic criterion for diabetes, but diabetes cannot be ruled out below 6.5%. When children suffer from diabetes, they should go to the hospital in time to improve the relevant examination and follow the doctor’s instructions to standardize the treatment.