The HCNH and CNH2 adsorption on different coordination sites of Cu(100) was theoretically studied considering the cluster approach. The present calculations show that the bridge site is the most favorite for CNH2 perpendicularly adsorbed on the Cu(100) surface via the C atom. For HCNH absorbed on the Cu(100) surface, the parallel adsorption mode with the C and N atoms nearly directly above the adjacent top sites of Cu(100) surface is the most favored. Both CNH2 and HCNH are strongly bound to the Cu(100) surface with CNH2 which is lightly stable (2.51 kJ(mol-1), indicating that both species may be co-adsorbed on the Cu(100) surface.