Objective: To investigate the application value of 24h holter electrocardiogram in the diagnosis of arrhythmia after pacemaker implantation. Methods: The clinical data of 65 patients who underwent pacemaker implantation in our hospital from October 2020 to October 2023 were retrospectively collected. The final diagnosis made by the third-level clinical physician based on the results of each examination is taken as the diagnostic gold standard. All patients underwent 12-lead electrocardiogram and 24h holter electrocardiogram. The detection results and diagnostic efficiency of the two methods for arrhythmia were analyzed and compared. The time domain parameters of Heart rate variability (HRV) in 24h holter electrocardiogram were compared between patients with and without arrhythmia. Results: Among 65 patients who underwent pacemaker implantation, 42 were positive and 23 were negative. The results of 12-lead electrocardiogram were positive in 26 cases and negative in 39 cases, which was generally consistent with the standard diagnosis results (Kappa=0.419, P < 0.001). The 24h holter ECG was positive in 40 cases and negative in 25 cases, which was consistent with the standard diagnosis results (Kappa=0.868, P < 0.001). The sensitivity and accuracy of 24h holter ECG in the diagnosis of arrhythmia were higher than that of 12-lead ECG, and the rate of missed diagnosis was lower than that of 12-lead ECG (P < 0.05). standard diviation of NN intervals in patients with arrhythmia SDNN), the number of adjacent R-R intervals > 50ms in the total number of NN intervals, (percent of NN 50 in the total number of NN intervals, PNN50) and root mean square of successive differences (RMSSD) between adjacent R-R intervals were lower than those in patients without arrhythmia (P < 0.05). Conclusion: 24h holter ECG is effective in diagnosing arrhythmia after pacemaker implantation, and HRV time domain parameters can provide evidence for clinical diagnosis.