The selective laser melting (SLM) technology is used to process the TiB2/S136 composites and the effect of laser energy density η on the densities, microstructures and mechanical properties of SLM-processed specimens is investigated. X-ray diffraction instrument, field emission scanning electron microscopy and transmission electron microscopy are used to study the phase compositions, surface morphologies and microstructures of specimens. The results show that, when η is low, the powders are not fully molten and thus a large amount of residual pores are formed. However, when η is too high, the micro-cracks are formed in the specimens because of thermal stress. When η is 66.7 J/mm 3, the specimens have less surface defects, their densities are up to 97.3%, and there exist fine and uniformly-distributed equiaxed grains. As for these specimens, the average micro-hardness is up to 742.4 HV0.1, and the average friction coefficient and wear rate are 0.5593 and 0.272×10 -4 mm 3·N -1·m -1, respectively, indicating an excellent abrasion resistance performance. The tensile strength is 1051.3 MPa and the elongation is 5.84%, indicating a relatively good plasticity. Above all, the optimal η for the SLM-processed TiB2/S136 composites is 66.7 J/mm 3, and if η is too high or too low, the densities and mechanical properties of TiB2/S136 composites would be seriously affected. This study provides a useful theoretical basis and a process guidance for SLM-processed high-performance die steels.