Laser melting was carryed out by HL-1500 CO2 lase rmachine on 40 Cr steel. The phase composition, microstructure, microhardness and corrosion resistance of the melting coating were investigated by means of scanning electron microscope, X-ray diffractometer, electrochemical test system, salt spray tester etc. The result showed that, melt zone、transformation hardened zone and the heat affected zone as mainly region in melting coating. Laser melting coating constitute by Fe3O4, Fe3C and martensite etc. The microstructure are mixed martensite and undissolved carbides, acicular martensite and retained austenite. The microhardness increased nearly twice as that of the 40Cr when scanning speed is 2.0 m/min. With the increase of the scanning speed, the corrosion resistance increased first and then decreased.