Abstract: Objective To investigate the correlation between glycemic variability and heart rate-corrected QT (QTc) interval in type 2 diabetes mellitus (T2DM) patients with diabetic kidney disease (DKD). Methods A total of 300 T2DM patients who were admitted in the Affiliated Hospital of Xuzhou Medical University from January 2018 to January 2020 were enrolled and their clinical data were retrospectively analyzed. According to the presence of renal complications, they were divided into two groups: a T2DM group (n=75) and a DKD group (n=225). According to estimated glomerular filtration rate (eGFR), patients in the DKD group were divided into four groups: a DKDⅠgroup (n=122), a DKD Ⅱ group (n=41), a DKD Ⅲ group (n=32) and a DKD Ⅳgroup (n=30). Then, QTc interval was estimated based on ECG results. Finally, according to QTc interval quartiles, patients in the DKD group were divided into QT1—4 groups, and the correlation between glycemic variability and QTc interval was analyzed. Results The DKD group presented remarkable increases in male percentage, alcohol drinking history, diabetes duration, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), triglycerides (TG), QTc interval, glycemic variability standard deviation of blood glucose (SDBG), the largest amplitude of glycemic excursion (LAGE), and postprandial glucose excursion (PPGE), the incidence of ST segment depression and insulin use rate, compared with the T2DM group (P<0.05). For the DKD group, with the decrease of eGFR, patients showed prolonged QTc interval and increases in glycemic variability (SDBG, LAGE, and PPGE). According to correlation analysis, glycemic variability (SDBG, LAGE, and PPGE) of the DKD group was positively correlated with QTc interval (r=0.477, 0.450 and 0.351,P<0.05). Multiple logistic regression analysis showed that SDBG was an independent risk factor of QTc interval prolongation. Conclusions With the aggravation of DKD, patients present increases in glycemic variability (SDBG, LAGE, and PPGE) and prolonged QTc interval. Glycemic variability (SDBG, LAGE, and PPGE) is positively related to QTc interval. SDBG is an independent risk factor of QTc interval prolongation in T2DM patients.