Abstract: Hastelloy X alloy was manufactured by selective laser melting (SLM) technique, and the effect of volumetric energy density(18.3,29.8,30.3,44.9,46.3,50.9,58.8,61.7,88.4 J·mm^-3) on micromorphology, microstructure, density and hardness of the alloy was investigated. The results show that the longitudinal section morphology of the Hastelloy X alloy manufactured by SLM was fish-scale-line morphology. Equiaxed crystals, dendrite and columnar grains spanning multiple deposited layers were present in the molten pool area, and the width of grains was about 0.6-1.2 μm. When the volumetric energy density was 18.3-46.3 J·mm^-3, there were pore defects in the alloy. As the volumetric energy density continued to increase, the pore gradually decreased and disappeared, and microcracks emerged and gradually increased. The density and hardness of the alloy increased first and then tended to be stable with the volumebric energy density increasing. The alloy with volumetric energy density of 50.9 J·mm^-3 had the least porosity and cracks, and the formability was the best.