Defects such as cracks and micropores exist in nickel-based superalloy during laser powder bed fusion (LPBF), hindering their application in various fields. Hot isostatic pressing (HIP) was combined with conventional heat treatment (HT) to obtain LPBF nickel-based superalloy parts with ideal properties and fewer defects. The results show that HIP process can improve the densification, while the conventional HT can eliminate the micro-defects to improve the mechanical properties. After HIP treatment, the defect volume fraction of LPBF specimens decreases. After HT, the defect content of HIP+HT specimens increases slightly. After post-treatment, the hardness shows a decreasing trend, and the tensile strength and post-break elongation of HIP+HT specimens increase to 1326 MPa and 21.3%, respectively, at room temperature.