Tetrabutylammonium perchlorate (TBAP) and propylene carbonate (PC) solution was used as catholyte electrolyte solution for CO2 reduction, and a novel two-chamber electrolysis cell was designed so that CO2 could be converted to CO in TBAP-PC solution, while water oxidation was carried out in the anode chamber. The results show that the electrochemical window in TBAP-PC electrolyte solution reaches -2.48 V (vs. I-/I3-), CO2 can be reduced to CO in TBAP-PC solution. The cathodic current density keeps stable at about 7.4 mA/cm2. The main gas evolved at the cathode is CO. Faradaic efficiency of CO formation reaches 93%. Owing to the presence of residual water in the catholyte, hydrogen is evolved at the cathode in competing with CO formation, Faradaic efficiency of H2 reaches 5%. There are no impurities adsorbed on the surface of Au electrode.