The effect of volume energy density on the relative density, microstructure and microhardness of Inconel 738 alloy fabricated by SLM was investigated by methods like SEM、 EBSD and OM. The results show that volume energy density the plays a decisive role in the SLM forming process. With the increase of the volume energy density, the relative density increases first and then decreases. The highest relative density (99.4%) can be achieved at 65.2J/mm3. During solidification, the microstructure of Inconel 738 alloy formed by 2.44×105 K/s SLM has obvious anisotropy in vertical direction and parallel direction. The microstructure parallel to the print direction is "chess board", the vertical to print direction is "fish scale", the overlap zone between layers and different tracks is the refined cellar grains. And the microstructure shows obvious texture, with the increase of the laser body energy density, the texture in the < 001 > direction increases gradually.The hardness of the sample increases with the increase of the laser body energy density. When the hardness value is higher than 65.2J/mm3, the hardness value of Inconel 738 alloy is higher than that of precision casting specimen (410 HV), hardness value is distributed on each surface independently.