AIM To investigate the cause of atrioventricular block(AVB) triggered by radiofrequency ablation(RFCA) in treatment of septal accessory pathway. METHODS We retrospectively analyzed the clinic features of patients who were cured by RFCA with septal accessory pathway. RESULTS The success rate for ablation of septal accessory pathway was 98.5%(66/67). AVB occurred in 3 of 66 patients(4.55%) which from second-degree block to third-degree block. CONCLUSION Although ablation of accessory bypass tracts is a successful and safe procedure, septal pathways bypass remain challenging. Accurate knowledge of cardiac electrophysiology and anatomy involved, precise mapping, lower ablation energy, enhancing catheter stability may reduce AVB.