Objective To explore the relationship between the monocyte to high-density lipoprotein choles-terol ratio(MHR)and atrial fibrillation(AF)in diabetes mellitus(DM)patients by analyzing the clinical da-ta.Methods A total of 132 patients diagnosed with DM in Linfen People's Hospital,the Seventh Clinical Col-lege of Shanxi Medical University from January 2018 to December 2023 were selected as group A,and 139 pa-tients with DM complicated with AF were selected as group B.The clinical data of the two groups were com-pared,and multivariate Logistic regression analysis was applied to identify the influencing factors of DM com-plicated with AF.The diagnostic value of MHR for AF in DM patients was evaluated by receiver operating characteristic(ROC)curve.Results There were statistically significant differences in age,hypertension,coro-nary heart disease,platelet count,neutrophils,lymphocytes,mean red blood cell volume,red blood cell volume distribution width,total bilirubin,conjugated bilirubin,unconjugated bilirubin,high-density lipoprotein choles-terol,neutrophil to lymphocyte ratio,and MHR between group A and group B(P＜0.05).The results of mul-tivariate Logistic analysis showed that MHR,age,hypertension,and coronary heart disease were independent risk factors for DM patients with AF(P＜0.05).ROC curve analysis showed that the area under the curve of MHR and the combination of age and MHR for diagnosing DM complicated with AF were 0.578(95％CI:0.510-0.646)and 0.811(95％CI:0.759-0.862),respectively.Conclusion MHR is an independent risk fac-tor for DM complicated with AF,and has good diagnostic value combined with age,which can be used to as-sess the risk of the occurrence of AF in the clinical management of DM patients.