Electrocatalytic CO2reduction reaction (CO2RR) has been extensively considered as a potential carbon cycle technology because it can use CO2as resources to produce high value-added fuels and chemicals under mild conditions. Therefore, developing highly efficient CO2RR catalysts is extremely significant. Here, we designed a series of TM-N2O2Cx(TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) single-atom catalysts and investigated their catalytic activities for CO2RR by using the density functional theory. Interestingly, these TM-N2O2Cxcatalysts exhibit excellent CO2RR selectivity towards three kinds of different products, including CH4, CO, and HCOOH at relatively low overpotentials, where the CO2RR product of Sc-N2O2Cx, Mn-N2O2Cx, and Zn-N2O2Cxis CO, and that of V-N2O2Cxis CH4, while the other six catalysts would produce HCOOH. Moreover, the best pathway for CH4formation is also unveiled, that is, * + CO2→ C*OOH → C*O + H2O → C*HO → C*HOH → C*H + H2O → C*H2→ C*H3→ * + CH4. In short, TM-N2O2Cxcatalysts exhibit high catalytic activity for electrocatalytic CO2RR, which provides useful information for experimental scientists to synthesize these promising CO2RR catalysts.