CO2 electrocatalytic reduction (CO2RR) to CO in organic electrolytes has received considerable attention due to its potential industrial application prospect. However, the reaction mechanism is not fully understood. In this study, we employed experimental observation, in-situ ATR-IRAS and Raman spectroscopy to elucidate the reaction mechanism of CO2 electro-reduction to CO in an organic medium. The reaction intermediates *CO2•-, *(CO2)2•- and *CO has been identified during CO2RR. Based on these results, the reaction mechanism has been discussed extensively. Density Functional Theory (DFT) analysis further indicates that the electrolytic CO2 reduction to CO in organic electrolyte is relatively more difficult than that in aqueous solutions.