Abstract: In this paper, the microstructure and its influence on mechanical properties of 316L stainless steel plate and 316L stainless steel formed by selective laser melting were studied. The differences in microstructure morphology, tensile properties at room temperature and high temperature were compared and analyzed under different processes. The test results show that the equiaxed grain structure can be seen in the stainless steel plate specimens by optical microscope (OM). in contrast, there are fish-scale molten pool morphologies in the SLM printed specimens, a large number of cell and fibrous subcrystalline structures can be observed after magnification. By electron backscatter diffraction (EBSD) analysis, a large number of equiaxed crystal structures and low angle grain boundaries can be seen in the stainless steel plate specimens. In contrast, the grain shapes of SLM printed specimens are mostly columnar crystal structures, and there are more high angle grain boundaries.In terms of tensile properties, the tensile properties of SLM-printed specimens at room temperature and high temperature are better than those of 316L stainless steel plate specimens.In terms of hardness, the hardness performance of SLM printed sample is higher than that of stainless steel plate sample.