Background Atrial arrhythmias occurring during the first 3-12 weeks (blanking period) after Radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF) can be highly symptomatic and often require an anti-arrhythmic drug (AAD), cardioversion or hospitalization. Objectives The anti-inflammatory effect of corticosteroid may suppress these atrial arrhythmias during blanking period after catheter ablation of atrial fibrillation. Methods We prospectively enrolled 83 patients who were randomly assigned to 2 groups (steroid and control group). The primary end points were atrial tachyarrhythmias or severe symptomatic PAC on regularly follow-up Holter monitoring at 12 lead ECG if patient had symptoms in post RFCA 6 months and clinical events (hospitalization and cardioversion) in 2 months after the ablation. Result During follow-up (median, 182 days), a total of 14 patients were hospitalized due to recurrent atrial tachyarrhythmias and cardioversion. There was no significant different in hospitalization and cardioversion between the two groups (18.4% vs 15.3% at 2 months; P=0.78). But the incidence of AAD administration to control symptomatic atrial arrhythmia was significantly lower in steroid group then in the control group (21.1% vs. 60.0% at 2 months; P<0.0001). After adjusting clinical and procedural characteristics, short-term steroid administration was independently associated with lower rate of atrial arrhythmias on Holter monitoring (adjusted HR 0.31, 95% CI 0.11-0.86, p=0.024). Conclusion Our data suggest that use of peri-procedural short-term corticosteroid significantly reduced the incidence of atrial tachyarrhythmias and the use of AAD during blanking period after catheter ablation of AF.