How high the fasting blood sugar can be operated needs to be judged according to the patient’s specific conditions, surgical methods and other factors, adult type 2 diabetes mellitus patients with ordinary surgery fasting blood glucose should be kept at 8~10mmol/L, fine surgery requires fasting blood glucose should be kept at 4.4~6.0mmol/L. Patients who need to undergo surgery with poor glycemic control are prone to postoperative infections, which also affects the patient’s postoperative blood glucose level, so they should actively control their blood glucose and its complications before surgery. Adult patients with type 2 diabetes need to control their fasting blood glucose at 8~10mmol/L before general surgery, and their blood glucose two hours after meal should be controlled at 8~12mmol/L; if they want to undergo fine surgery, their fasting blood glucose should be controlled at 4.4~6.0mmol/L, and their blood glucose two hours after meal should be 6~8mmol/L. For simple stress hyperglycemia or non-elderly patients in good physical condition without the risk of cardiovascular and cerebrovascular complications, preoperative fasting blood glucose should be controlled at 6~8mmol/L, and blood glucose two hours after meal should be controlled at 8~10mmol/L. Patients who need to undergo surgery should actively cooperate with their doctors to control their blood glucose before surgery, and consult the doctor promptly if they feel unwell.