Abstract: Metal matrix composite layer reinforced in situ ZrC particles was formed by laser cladding overlapping on the medium carbon steel.The morphology, microstructure, interface structure and the distribution of the ZrC particles were observed with optical microscope, scanning electron microscope (SEM) and EDAX.The microstructural characteristics of ZrC reinforced metal matrix composites are the typical y austenite dendrite and cellular distributed on the eutectic substrate.Most of the dispersed,ultrafine ZrC particles are uniformly distributed within dendritic and interdendritic regions owing to the trapping effect of the advanced solid liquid interface.The martensite transformation is observed after the rapid cooling processes also.The microstructuml characteristics of the interface between the coating and the substrate are martensite transformation which shows that there is good metallurgical bonding.With the overlapping scanning speed increases,the orientation of the dendrite becomes tobulence,the quantities of the martensite transformation increase,the sizes and the quantities of ZrC particles become larger and more.