Abstract In this study, WC‐Ni/high‐speed steel composite materials for application as micro‐drills were prepared by cold pressing and high‐temperature vacuum sintering using a self‐designed mold in the laboratory. The effect of Ni on the microstructure and diffusion behavior at the interface of the WC/high‐speed steel composite was investigated. The results show that the addition of Ni pro-moted the diffusion of elements, and reduced defects such as micropores and microcracks at the WC/high‐speed steel composite interface. It also improved the bonding strength of the WC/high-speed steel composite interface, and significantly decreased the WC hardness.