Abstract: The 40Cr steel has been surface-alloyed with a pre deposited carbon powder layer by laser beam.White cast iron is obtained on the surface of the sample with a depth of 0.25～0.35mm.The microstructure of the melted zone is pre-dendrite and eutectic ledeburite whose size is obviously refined by the rapid quench.Its micro hardness can get up to 1200HV0.3.The microstructure of the heat-affected zone is martensite with two sub-layers,one of which is pin-like martensite and the other,no-pin martensite.It indicates that the higher the scanning speed and power density,the smaller the grain,and therefore the higher the micro hardness.The wear test shows that the wear resistance of the specimens has been encreased by 50% than the general quenched samples.