In this study, we first demonstrate that CO production selectivity from CO2 on Au electro-catalyst depends on the type of electrolyte anion. Comparing the faradaic efficiencies of H-2, HCOO- and CO in the presence of different anions such as Cl-, HPO42-, SO42- and HCO3- at constant potential of -0.7 V (vs. RHE), we observe that the CO/H-2 ratio could be enhanced due to strongly adsorbed anion such as Cl-. Although HPO42- is more strongly adsorbed than SO42- and HCO3- on the surface of electrode, CO2 reduction in HPO42- containing solution exhibited a minimum faradaic efficiency of CO (11%) but a maximum faradaic efficiency of H-2 (70%). Based on physicochemical analytical tools (LSV, EIS, SEM, XPS and XRD) and according to previous studies, we conclude that the product distribution is associated with distinct properties caused by characteristic of each anion when adsorbed on the electrode surface such as specific adsorption strength and intrinsic characteristic of anions.