Electrochemical CO reduction reaction (CORR) is an efficient way in the utilization of CO. In this work, single transition-metal (TM) atom (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) anchored on two-dimensional (2D) TiCN are designed for CORR using density-functional-theory (DFT) calculation. We show that TiCN serves as an excellent substrate to support single atom catalysts (SACs), compared to TiCO and TiCF. We find that the Sc, Ti and V supported on TiCN show high catalytic activities to produce CO with a low overpotential of 0.37, 0.27, and 0.23 eV, respectively. Differently, the Mn and Fe on TiCN are catalytically active for the production of HCOOH with a low overpotential of 0.32 and 0.43 eV, respectively. We further show that the negatively charged TM-TiCN can capture and activate CO more effectively, and the catalytic activity and selectivity can be significantly tuned by injecting extra electrons.