Abstract: The laser alloying of 45,carbon steel surface with chromium and nickel using 1.1 kW CO2 laser has been realized. Through analysing content of alloying elements and phase structure of the alloyed layer, measuring microhardness and wear resistance of substrate and alloyed layer, it has been shown that the structure of alloyed layer is a cellular dendrite and the phases of alloyed layer consist of martensite and residual auste-nite. This phase constitution is decided upon the content of elements (Cr, Ni) contained in alloyed layer and solidifying speed accompanied by high-speed cooling during the alloying. The test results showed that the microhard -ness of alloyed layer is 2-3 times of that of 45* carbon steel substrate, and the wear resistance of the former is much better than the original.We considered that the improving of the wear-resistance of the alloyed layer is related to the increase of the surface hardness.