Abstract: High hardness composite chromium carbide was successfully produced by in situ synthesis technology, which make it possible to prepare high temperature wear resistance alloy.Chemical reaction among Cr, Fe and C powder which were mixed and laid on the metal surface occurred through vacuum electron beam rotary scanning heating.The resultant of reaction at the metal was identified as Cr₇C₃ composite by X-ray diffraction.And microstructure of composite shows that there is chromium carbide congregated at the metal surface.The mechanical properties show that surface hardness is higher than that of base metal because of chromium carbide.In situ synthesis technology was proved to be a good way to realize metal surface modification.