Abstract: The samples were prepared by selective laser melting equipment in the presence and absence of reflux. Then, the microstructure, phase and fracture of the printed parts were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD).The results show that the phase of the two formed parts is austenite phase, and the microstructure presents cellular crystals.Under the influence of rapid non-equilibrium solidification and Marangoni convection, the crystal orientation of the cellular crystal exhibits anisotropy. The surface of the part prepared in the absence of reflux is smooth and neat; there are many micron-level particles on the surface of the part prepared in the reflux state, and the melt channel is partially interrupted. After the deep corrosion, holes and unmelted powder can be observed inside. There are a large number of equiaxed dimples in the fracture of the part prepared without reflux. The dimples in the fracture of the part prepared in the reflux state show the shape of “pumpkin”, and many holes can be observed in the fracture. By comparing those of the sample without reflux, the tensile strength of the sample in the presence of reflux is reduced by 51.98 MPa and the elongation is reduced by 7.39%. The internal defects such as slag inclusion, unmelted particles and holes in the part prepared in the presence of reflux reduce the bearing area of the sample, which causes stress concentration and reduces the mechanical properties of the part.