Catheter ablation is the only choice of treatment in some small children with medically refractory supraventricular tachycardia (SVT). Electroanatomical mapping systems (EMS) are more commonly utilized in electrophysiological procedures in recent years, which resulted in a significant decrease in fluoroscopy exposure. The potential benefit of EMS in small children has not been studied. Therefore, we investigated the outcomes of children undergoing catheter ablation weighing ≤ 20kg using an electroanatomical mapping system. This study evaluated the outcomes, characteristics, and follow-ups of children ≤ 20kg who underwent SVT ablations between April 2012 and April 2018 in a pediatric electrophysiology center where EMS were routinely used. In a 6-year period, 1129 children underwent SVT catheter ablation under EMS guidance at our institution. A total of 84 of them were weighing ≤ 20kg. The acute success rate was 97.6% in 85 tachycardia substrates. No fluoroscopy was used in 58 of the patients, while a median of 5 (4-14)min of fluoroscopy was used in the remaining 26 patients. Recurrences were seen in 4 patients (4.8%) at a mean follow-up of 3.89 ± 2.08years. Five patients developed non-vital complications (2 right bundle block and 3 temporary complete block that spontaneously resolved during the procedure). The outcome of catheter ablation with the guidance of EMS for the treatment of SVT in small children is favorable. Fluoroscopy exposure can be decreased and even eliminated in most patients.