Inconel 718 pre-alloyed powder was prepared by electrode induction melting gas atomization (EIGA). Powder metallurgy (PM) Inconel 718 alloy was formed by hot isostatic pressing (HIP) + special high temperature heat treatment (SHT) and then its microstructure was observed and its mechanical properties were tested. The results show that the SHT can reduce prior particle boundaries (PPBs) and improve the elongation and impact toughness of PM Inconel 718 alloy. Based on the SHT, the holding time of the high-temperature section is extended and the HIP is optimized. The optimized process can inhibit or eliminate PPBs in PM Inconel 718 alloy, increase the number of twins, and improve the alloy properties. The tensile elongation at 650 ℃ has been increased from 6% to 10%. The optimized HIP can be used as an alternative process to HIP + SHT to achieve near-net-shape and achieve the purpose of cost reduction and efficiency increase.