Abstract: Fe/Cr/C powder mixtures were employed to modify the surface of a low carbon steel substrate by electron beam irradiation in vacuum condition.By optimizing the electron beam parameters, chromium carbide is in situ synthesized in the surface composite layer.The surface composite layer was analyzed with optical microscope, XRD analysis and trobological test.There are two main phases in the surface composite layer :chromium carbides as hard phase and austenite as tough phase.There are little typical hexagonal primary chromium carbides in the surface composite layer.Eutectic chromium carbides dispersively distribute between the interface of austenite phase to form a net like structure.It is metallurgical combination in the surface composite layer and the substrate.The existing of carbides in the composite layer provides a notable improvement on the wear resistant property of the surface layer.