Background / Aim The incidence of atrial fibrillation(AF) in patients with atrioventricular block (AVB) appears increased over that for the unpaced population even if atrioventricular synchrony is maintained by dual chamber pacing. . But AVB patients after synchronized pacemaker insertion, the risk of AF reduces or not is still questionable. The p-wave duration (PWD) and late potential (LP) on signal averaged electrocardiogram (SAECG) are a non-invasive markers of intra-atrial conduction disturbances, which are believed to be the main electrophysiological cause of AF. The aim of this study was to investigate the change of PWD on baseline and after 6 month on SAECG to see the increase or decrease of AF risk. Methods A total of 8 patients with insertion of VDD or DDD pacemaker were enrolled in the study. 3 were inserted with VDD and 5 person was inserted with DDD. All patients P-wave SAECG was recorded at 2009.12 and was follow up after 6months. Results The baseline of mean of PWD on SAECG was 204.8ms. After 6months follow up mean of PWD on SAECG was 176.8ms. The change of PWD was 28(13.7%,p value = 0.19)ms. At VDD group the baseline PWD was 244.3ms and reduced to 237.3ms after 6months. The change was 7(2%,p value = 0.5)ms. In DDD group the baseline of PWD was 181.2ms and reduced to 140.6ms. The change was 40.6(22.4%, p value = 0.1)ms. Conclusion PWD on SAECG decreased after 6 months follow up. There was no statically significancy in AVB patients after synchronized pacemaker insertion. But the PWD was decreased after synchronized pacemaker insertion and may decrease AF.