Electrocatalytic CO2 reduction has received great attention for alleviating environmental problems and energy crisis. SnO2-based catalysts are attractive candidates, but they still face problems such as high overpotentials and small current density due to their low intrinsic electrical conductivity and weak activation for CO2. Here, superior selectivity and activity for C1 products (HCOO- and CO) were obtained using In-doped SnO2. The maximum faradaic efficiency was 96.46% at -0.75 V and the partial current density reached -20.12 mA cm-2 at -0.95 V for C1 products. Furthermore, the selectivity for C1 products was over 90% from -0.5 to -1.0 V with a current density of -166.2 mA cm-2 at -1.0 V in flow cells. In ion doping induced electron transfer from Sn species to In and simultaneously generated oxygen vacancies, which improved electrical conductivity and regulated the oxidation state of Sn active sites and provided more active sites. This work emphasizes the role of enhanced electron transfer of catalysts in CO2 electroreduction.