ObjectiveTo evaluate the incidence of postoperative atrial fibrillation (POAF) after dexmedetomidine and diazepam in patients undergoing coronary artery bypass grafting (CABG). MethodsA retrospective cohort study was conducted in the patients who underwent CABG in the General Hospital of Northern Theater Command from October 2020 to June 2021. By propensity score-matching method, the incidence of POAF after dexmedetomidine and diazepam application in patients undergoing CABG was evaluated. ResultsFinally 207 patients were collected, including 150 males and 57 females, with an average age of 62.02±8.38 years. Among the 207 patients, 53 were treated with dexmedetomidine and 154 with diazepam before operation. There was a statistical difference in the proportion of hypertension patients and smoking patients between the two groups before matching (P<0.05). According to the 1∶1 propensity score-matching method, there were 53 patients in each of the two groups, with no statistical difference between the two groups after matching. After matching, the incidence of POAF in the dexmedetomidine group was lower than that in the diazepam group [9.43% (5/53) vs. 30.19% (16/53), P=0.007]. There was no death in the two groups during hospitalization, and there was no statistical difference in the main adverse events after operation. The ICU stay (21.28±2.69 h vs. 22.80±2.56 h, P=0.004) and mechanical ventilation time (18.53±2.25 h vs. 19.85±2.01 h, P=0.002) in the dexmedetomidine group were shorter. Regression analysis showed that age, smoking and diabetes were related to the increased incidence of POAF (P<0.05), and preoperative use of dexmedetomidine was associated with a reduced incidence of POAF (P=0.002). ConclusionFor patients undergoing CABG, the incidence of POAF with dexmedetomidine before operation is lower than that with diazepam. Preoperative application of dexmedetomidine is the protective factor for POAF, and old age, smoking and diabetes are the risk factors for POAF.