A new planar isomer of HNC3 system, H-cCNC-C, is theoretically predicted by means of B3LYP and CCSD(T) methods. The suggested species can isomerize into other five kinetically more stable isomers, which have been experimentally identified, with relatively higher reaction barriers. In view of its higher kinetic stability, we can reasonably believe that the obtained species H-cCNC-C can be experimentally observed in future studies.