Abstract: A simple fcc Cr carbide was formed for the firal time by carbon ion implantation into Cr thin filma. Lattice constant determined by electron diffraction was 0.403nm. In situ annealing in TEM showed it exited upto a temperature about 250℃. The carbide phase was further confirmed by Auerg electron spectra. The meidema heat of formation was - 29.4kJ/mbl.