Abstract: Surface melting of alloy cast iron with the light beam of a xenon lamp, microstructures and properties of melted layer and the influence of light beam parameters on them were investigated. The results show that melted layer of white iron with a depth of millimeter level and micro hardness of 850 kgf/mm² can be obtained on the surface of cast iron by using the light beam. The depth and width of melted layer can be controlled effectively through adjusting the density of light power and scan rate. A single pass melting width can be up to 12 mm, when the input power is 5kW and scan rate is 3.5m/h. The light beam melted zone of alloy cast iron obtains a lamellar structure. At the lower scan rate the melted layer consists of a carbon poor zone with very low hardness in its surface, a sub eutectic ledeburite in its middle and a mixture with ledeburite and graphite eutectic at its bottom. The lose of carbon can decrease with increasing of light beam scan rate and therefore the carbon poor zone is inhibited.