Hard composite materials are often used as alloy materials for tool production due to their high hardness, high strength and good wear resistance. In this paper, selective laser melting (SLM) technology was used to prepare WC 12Co cemented carbide samples by changing the forming process parameters, laser power and scanning speed, and the effects of process parameters on the density, cross-section metallographic structure and microhardness of the formed samples were studied. Results show that when the laser scanning speed value is constant, with the increase of the laser power, the density of the molded sample shows a gradually increasing trend. When the laser power value is constant, with the increase of the laser scanning speed, the density of the molded sample first increases and then decreases, and the scanning speed has a more obvious influence on the density; too large or too small line energy density is not conducive to the increase of the sample density. When the laser power is 290 W, the scanning speed is 900 mm/s under the optimal parameter combination, a WC 12Co sample with a density of 91.392% was obtained. Through reasonable matching design of process parameters, it provides theoretical and process practical reference for the application of SLM molding WC 12Co in actual industrial production.