Relationship between the melting depth and laser parameters in laser melting treatment of Fe2B boronized layers and phase distribution of 45* steel is studied. It was found that: (1) the melting depth H is related to the scanning speed v as H=K/v0.65, at a given laser power density; (2) there is FeB phase in a melted zone; (3) curve of hardness distance from the surface has a hardness peak and the position of which depends on the scanning speed.