Abstract: High current pulsed electron beam combined with magnetron sputtering had been employed to fabricate Cr alloying layer on M50 steel. Scanning electron microscope, transmission electron microscope, and X-ray diffraction had been used to analyze the microstructure of the Cr alloying layer. The tribological properties and wear mechanism of the Cr alloying layer were studied. The results show that the Cr alloying layer possessed multi-layer characteristics. The Cr alloying layer was composed of BCC Fe-Cr, γ phases and martensite. The wear mechanism of M50 steel and Cr alloying layer was oxidation wear. The friction coefficient of the Cr alloying layer was between 0.2~0.4, lower than that of M50 steel (0.5~0.8). The reason was the solid lubrication effect of the oxides and the good adherence between the oxides and Cr alloying layer which can be concluded by the results of scanning electron microscope and energy dispersive spectrometer.