Background CartoMerge has been widely used in guiding circumferential pulmonary vein isolation (CPVI) for the treatment of paroxysmal atrial fibrillation (PAF).However, the procedure of landmarks selection varies among operators according to their experience.Techniques have to be established to standardize this procedure.We propose that Overlay Ref could facilitate this procedure.This paper aimed to report our initial experience with CPVI guided by Overlay Ref and CartoMerge for the treatment of PAF.Methods Fifty-nine patients with PAF were enrolled in this study.Using Overlay Ref technique, a reference image (inverted) was faded into the live fluoroscopic image.Landmarks of CartoMerge were selected from anatomic points of the top of superior pulmonary veins (PVs) and the bottom of inferior PVs guided by Overlay Ref image.Overlay Ref images were also used to guide the ablation procedure combining with CartoMerge.Results All patients were successfully mapped by CartoMerge guided by Overlay Ref.The distance between the mapping points and the CT surfaces was (1.42±0.67) mm for the patients as a whole.This led to a successful rate of 96%for isolation of pulmonary veins.Duration of ablation procedure was (92±17) minutes.And the total duration of procedure was (139±32) minutes.CartoMerge could also be performed just with 3 paries to 4 paries selected landmarks guided by Overlay Ref without a full anatomic model constructed by Carto.Then, the total duration of procedure could be shortened to (115±38) minutes.Conclusions Overlay Ref technique can facilitate the catheter ablation of PAF and can help to standardize the procedure of landmarks selection.