Objective To explore the predictive value of monocyte count to high-density lipoprotein-cholesterol ratio (MHR) for new atrial high-rate episodes (AHREs) in patients with bradycardiac arrhythmia after dual-chamber pacemaker implantation. Methods The data of patients implanted with dual-chamber pacemaker in the First Hospital of Hebei Medical University from Jun. 2013 to Jun. 2018 were retrospectively analyzed. According to the inclusion and exclusion criteria, 140 patients were finally included. The patients were followed up for 12 months, and then divided into AHREs group and non-AHREs group according to whether AHREs occurred during the follow-up period. The general characteristics and the laboratory indexes were compared between the two groups. Furthermore, all patients were divided into MHR<3.26 group, MHR 3.26-5.00 group and MHR>5.00 group. Cox proportional hazards regression analysis was used to analyze the risk of AHREs. Results The median age of the patients was 70.00 (61.00, 75.00) years. AHREs were detected in 28 patients during the follow-up. There were significant differences in white blood cell count, neutrophil count, monocyte count, high-density lipoprotein-cholesterol and MHR in the patients with AHREs compared with the non-AHREs group during the follow-up (all P<0.05). Multivariate Cox proportional hazards regression analysis showed that MHR (HR=1.537, 95% CI 1.209-1.955, P<0.001) increased the risks of new AHREs after dual-chamber pacemaker implantation. Compared with the MHR<3.26 group, the risk of AHREs in the MHR 3.26-5.00 group (HR=1.811, 95% CI 0.366-8.958, P=0.467) had no significant change, while the risk of AHREs in the MHR>5.00 group (HR=10.128, 95% CI 2.051-50.003, P=0.004) was increased significantly. Conclusion As a new marker of inflammation and oxidative stress in blood, high MHR increases the risk of new AHREs in patients with bradycardiac arrhythmia after dual-chamber pacemaker implantation.