Abstract: Four line rotation scanning” vacuum electron beam was used in this test. Different natures of surface composite layers were in situ synthesized on the lowalloy steel, with four different ratio of Fe/Cr/C alloy powder. Each deposited sample was analyzed with optical microscope (OM), scanning electron microscope (SEM), Xray diffraction (XRD) and surface microhardness testing to study the effect of powder composition on the surface composite layer’s microstructure and mechanical property. The results show that the microstructures of surface composite layers prepared by different ratio Fe/Cr/C powder mixtures vary significantly. As the carbon content increases, the amounts of carbides will be formed higher, and the hardness also increases. The microstructures of the composite layers are martensite structure, hypoeutectic microstructure, eutectic structure and hypereutectic microstructure. It provides an important basis for the FeCrC material to have excellent wearresisting property.