Porous diamond grinding tools are a new-type tools that can provide a space for chip holding and coolant flowing during the grinding process. Selective Laser Melting (SLM), as a typical additive manufacturing technology, is an effective method to fabricated porous diamond tools. However, due to the limitations of spot size and layer by layer fabricating process in SLM process, the designed porous diamond tools are difficult to be manufactured accurately. Therefore, it is necessary to investigate the manufacturing process constraint of feature structures. Based on CuSn20/diamond composites, a series of feature structures such as overhang structures, thin-walled, holes, and sharp angle structures with different fabricating directions and sizes were fabricated by SLM technology. The formability, forming errors, and causes of these structures are analyzed. The results show that the optimal formable length of the overhang structure is 1-2 mm; The minimum formable size of thin wall structures is 0.70 mm; The minimum formable diameter size of hole structures perpendicular to the fabricating direction is 0.20 mm; The optimal forming diameter size for circular hole structures parallel to the fabricating direction is 0.50-3.00 mm; The formable angle of sharp angle structures should be greater than 10 °. The forming error of feature structures is mainly affected by the thermal adsorption of laser on composite powder, the diffusion of laser spot heat affected zone, and the weak support of composite powder. This work provide a certain technical reference for the design and additive manufacturing of complex diamond tools.