Mechanical properties of the SLM 316L sample have significant anisotropy. The impact absorbing energy of the sample prepared at room temperature is about 47% and 44% of that of the rolled plate, respectively, when the sampling direction is in the horizontal direction and the vertical direction. The tensile strength of the SLM samples prepared at room temperature under a vertical load is about 81.6% of that under a horizontal load. Preheating has little effect on the relative density and impact toughness. Preheating reduces microhardness by about 4%. After preheating, the tensile strength of the 316L sample formed by SLM decreases by about 4% and the elongation increases by about 6%. Under the experimental conditions in this paper, preheating has little effect on the fatigue life of the sample under a vertical load, but significantly improves the fatigue life of the sample under a horizontal load. The main reason may be that preheating can inhibit the formation of large-size defects.