To investigate the impacts of process parameters on the cracking behavior, porosity, and microstructure, an SRR99 nickel-based superalloy was fabricated by selective laser melting (SLM) technology. The results show that high-density samples can be prepared by setting reasonable scanning velocity, hatch spacing, and layer thickness under the fixed laser power. The laser volume energy density is the main parameter that affects crack and porosity of the SRR99 nickel-based superalloy. The number and size of cracks increase sharply as the laser volume energy density rises. It is found that most of the cracks originate in the interface of cladding layers and propagate along intergrain boundaries. At the same time, the pores are irregularly shape when the laser volume energy density is inadequate, whereas they gradually transform from irregularity to roundness with the increase of the laser volume energy density. The microstructures of the SLM deposition samples are superfine columnar dendrites. In addition, the primary dendrite spacing increases slightly with the increase of building height, and secondary dendrite arms are underdeveloped.