Ni/WC surface infiltrated composite layer was fabricated on gray iron substrate through vacuum infiltration casting technique using Ni-based powder and WC particles with different content as raw materials. The compact infiltrated composite layer was obtained on the condition of appropriate choice of processing condition such as pouring temperature, preheating temperature, thickness of preform and the grain size of powder. The infiltrated layer includes surface composite layer and transition layer, and the thickness of transition layer decreases with the increasing content of WC. Three-point bending tests were performed to investigate the mechanical and metallurgical properties of the surface infiltrated composite layer. It was found that load-holding circumstance appeared for specimen with infiltrated layer during the process of three-point bending, and there was no this circumstance for substrate during bending process. The load and displacement decreased with the increasing content of WC when the load-holding circumstance happened. The fracture extended to the substrate for all specimens with surface infiltrated composite layer, and the fracture form was similar for all specimens with different WC content. The WC particles were the source of micro-crack for surface infiltrated layer, and the graphite was the source of micro-crack for gray iron substrate.