Abstract: Selective laser melting (SLM) formed Hastelloy X alloy samples were treated by hot isostatic pressing (HIP) with parameters of 1 100℃/100 MPa/1 h, 1 175℃/160 MPa/1 h, 1 175℃/160 MPa/2 h and 1 175℃/100 MPa/2 h, respectively, and then subjected to stress-rupture tests at 815℃ under 105 MPa. The effects of HIP process on microstructure and stress-rupture property were studied. The results show that before HIP treatment, the microstructure of the sample was composed of fine columnar crystal and dendrite. After HIP treatment, the grains became larger and carbides precipitated at grain boundaries. After HIP treatment at 1 175℃, the elongation and reduction of area of the sample were higher than those before HIP treatment and after HIP treatment at 1 100℃, and the anisotropy of the microstructure and stress-rupture property decreased. The relatively long HIP time or relatively low HIP pressure decreased the rupture time, elongation and reduction of area of the sample. When the HIP process parameters were 1 175℃/160 MPa/1 h, the stress-rupture property of the sample was relatively good, and the eliminating of cracks was relatively effective.