In this study, Inconel 625 superalloy (IN625) samples were formed using the selective laser melting (SLM) technology. The effects of the process parameters on defects, such as pores and cracks, were investigated. Then, the microstructure and mechanical properties of the samples under the optimal relative density were analyzed. Results show that the samples has a relative density of over 99.5% when the energy density is 50-78 J·mm ^-3. An energy input of approximately 75 J·mm ^-3 is required to approach the completely dense state. The sample displays cracks and un-melting powder owing to the low energy density. When the energy density is high, irregular and fine pores appear. The IN625 sample morphology shows cellular and columnar grains. Meanwhile, the average size of grains is 10-30 μm and the number of subgrains is small. The <001> crystallographic orientation is the preferred direction for the IN625 samples. A large number of small dimples appear on the mixed fracture. The microhardness, tensile strength, yield strength, and elongation are (327±3) HV, (930±5) MPa, (700±5) MPa, and 29.5%, respectively.