ObjectiveTo explore the effect of ablation of left superior pulmonary vein fat pad(LSPV-FP) on atrial fibrillation(AF). MethodsTwelve healthy adult mongrel dogs were anesthetized and ventilated; both cervical vagosympathetic trunks were exposed for stimulation. Thoracotomies at the 4th intercostal space of left and right chest were performed to expose the LSPV-FP. The effective refractory period(ERP)/ERP-dispersion (dERP) of atrium and LSPV, AF inducibility, and the ventricular rate of AF were measured in the following statuses: baseline, vagosympathetic trunk stimulation(VTS), LSPV-FP ablation, and VTS post LSPV-FP ablation. ResultsAt baseline status, stimulation of the left or right vagosympathetic trunks significantly shortened the ERP of atrial ( \[84.44±29.50\] ms vs \[129.7±15.83\] ms, \[85.42±26.11\] ms vs \[129.7±15.83\] ms, P<0.05), increased the dERP of atrial ( \[71.67±14.03\] ms vs \[34.17±18.32\] ms,\[57.5±24.17\] ms vs \[34.17±18.32\] ms, P<0.05), the difference of ERP between proximal and distal of LSPV(P<0.05),AF inducibility ( \[5.33±1.231\] times vs \[0.75±0.96\] times, \[4.67±1.155\] times vs \[0.75±0.96\] times, P<0.05), and deceased the ventricular rate of AF(\[143.6±22.42\] beats/min vs \[226.3±28.50\] beats/min, \[146.4±30.72\] times/min vs \[226.3±28.50\] times/min, P<0.05). LSPV-FP ablation significantly attenuated all the above electrophysiological changes induced by left VTS(P<0.05), but showed no effects on those induced by right VTS. Conclusion Left vagosympathetic trunk plays an important role in the development and maintenance of AF partially through LSPV-FP.