Electrocatalytic reduction of CO2 is a promising route for energy storage and utilization.Herein we synthesized SnO2 nanosheets and supported them on N-doped porous carbon (N-PC) by electrodeposition for the first time.The SnO2 and N-PC in the SnO2@N-PC composites had exellent synergistic effect for electrocatalytic reduction of CO2 to HCOOH.The Faradaic efficiency of HCOOH could be as high as 94.1% with a current density of 28.4 mA cm-2 in ionic liquid-MeCN system.The reaction mechanism was proposed on the basis of some control experiments.This work opens a new way to prepare composite electrode for electrochemical reduction of CO2.