Backgrounds: Diabetes mellitus is an independent risk factor for Contrast-induced nephropathy (CIN) in patients undergoing Coronary arteriography (CAG)/percutaneous coronary intervention (PCI). Glycosylated hemoglobin (HbA1c) is the gold standard to measure blood glucose control, which has important clinical significance for evaluating blood glucose control in diabetic patients in the past 3 months. This study aimed to evaluate whether preoperative hemoglobin a1c levels in diabetic patients who received CAG/PCI had an impact on the occurrence of postoperative CIN.Methods: We reviewed the incidence of preoperative HbA1c and postoperative CIN in 670 patients with CAG/PCI from January 1, 2020 to October 30, 2020, and divided the preoperative HbA1c levels into 5 groups. Blood samples were collected at admission, 48h and 72h after operation to measure the Scr value of patients. Categorical variables were compared using a chi-square test, and continuous variables were compared using an analysis of variance. Fisher’s exact test was used to compare the percentages when the expected frequency was less than 5. Multivariable logistic regression analysis was used to exclude the influence of confounding factors and P for trend was used to analyze the trend between HbA1c levels and the increased risk of CIN. Results: Patients with elevated HbA1c had higher BMI, FBG and LDL-C, and they were more often on therapy with hypoglycemic agents, Insulin and PCI. They also had higher basal, 24h and 48h Scr. (Table 1) The incidence of CIN in the 5 groups of patients were: 9.8%, 11.9%, 15.2%, 25.3%, 48.1%. (p<0.0001) The multivariate analysis confirmed that in the main high-risk subgroup, patients with elevated HbA1C levels (≥8.8%) had a higher risk of CIN disease. (Figure 2) Trend test showed the change of HR (1.000,1.248,1.553,2.625,5.829). (Table 2)Conclusions: Studies have shown that in diabetic patients undergoing CAG/PCI, elevated HbA1C is independently associated with the risk of CIN, and with the increase of HbA1C level, the incidence of CIN gradually increases.