Abstract: Fe-based composite layers reinforced by in situ ZrC particles were formed by laser overlapping and single cladding using preplaced FeCSiB alloy powders on a medium carbon steel matrix. The morphologies,microstructures,interface structure and the distribution of the ZrC particles in the clad layers were observed with optical microscopy,field emission electric scanning microscopy (FEEM). The microstructure of ZrC-reinforced Fe-based composite layers is the typical γ austenite dendrite and cellular distributed on the eutectic substrate. The energy dispersive spectroscopy (EDS) analysis shows the reinforcements are in situ synthesis carbides which main compositions consist of transition elements Zr,Mo and carbon. The compound carbide particles distributed within dendrite and interdendritic regions with 1.96%,2.2%～3.84% volume fractions for single and overlapping layers respectively. The martensite transformation went with the rapid cooling processes also. The Fe-based composite layers are dense and free of cracks with a good metallurgical bonding between the layer and substrate. The microhardness values across layer cross section vary between 800HV0.2～1100HV0.2.