Background The origin distribution of right-ventricular-outflow-tract (RVOT) ventricular arrhythmias (VAs) remains unclear. There is limited data on the ablation effectiveness of the reversed U-curve method compared with the antegrade method. Objectives To investigate the origin distribution of RVOT-type VAs and compare the ablation effectiveness of the two methods. Method Consecutive patients who had idiopathic RVOT-type VAs were prospectively enrolled. After activation mapping, patients were randomly assigned to supravalvular strategy using the reversed U-curve or subvalvular strategy using the antegrade method. The primary outcome was initial ablation (IA) success, defining as the successful ablation within the first three attempts. Results 61 patients were enrolled from November 2018 to June 2020. Activation mapping revealed 34/61 (55.7%) of the earliest ventricular activating (EVA) sites were above the pulmonary valves (PVs). The IA success rate was 25/33(75.8%) in the patients assigned to supravalvular strategy as compared with 16/28(57.1%) in those assigned to subvalvular strategy (P=0.172). Logistic regression revealed a substantial and qualitative interaction between the EVA sites and IA strategies (Pinteraction<0.001). For multiple-comparison, either strategy had a remarkably higher IA success rate in treating its ipsilateral EVA sites than contralateral ones (P<0.0083). Conclusion Of the idiopathic RVOT-type VA origins, half were located above the PV. The two strategies did not differ in the primary outcomes. However, they complement locating the EVA sites and facilitate ipsilateral ablation, which produces a significantly higher IA success rate. (Chinese Clinical Trial Registry number, ChiCTR2000029331)