Electrochemical reduction of CO2 to value-added chemicals and fuels shows great promise in contributing to reducing the energy crisis and environment problems. This progress has been slowed by a lack of stable, efficient and selective catalysts. In this paper, density functional theory (DFT) was used to study the catalytic performance of the first transition metal series anchored TM-Bβ12 monolayers as catalysts for electrochemical reduction of CO2. The results show that the TM-Bβ12 monolayer structure has excellent catalytic stability and electrocatalytic selectivity. The primary reduction product of Sc-Bβ12 is CO and the overpotential is 0.45 V. The primary reduction product of the remaining metals (Ti-Zn) is CH4, where Fe-Bβ12 has the minimum overpotential of 0.45 V. Therefore, these new catalytic materials are exciting. Furthermore, the underlying reaction mechanisms of CO2 reduction via the TM-Bβ12 monolayers have been revealed. This work will shed insights on both experimental and theoretical studies of electroreduction of CO2.