Defects such as cracks and micropores existed in nickel-based superalloy during laser powder bed fusion (LPBF), hindering their application in various fields. In this paper, hot isostatic pressing was combined with conventional heat treatment to obtain LPBF nickel-based superalloy parts with fewer defects and ideal properties. The hot isostatic pressing process improved the densification, and the conventional heat treatment changed the micro-defects to improve the mechanical properties. After HIP treatment, the defect volume fraction of LPBF specimens decreased to 0.0132%, after HT treatment, the HIP+HT specimens defect content rebounded to 0.0252%. After post-treatment, the hardness showed a decreasing trend, and the tensile strength and elongation at break of HIP+HT specimens increased by 32.2% and 474.7%, respectively, at room temperature.