Powder metallurgy (P/M) Ni-based superalloy has been the most important material for high-temperature structural application in turbine disc owing to its good tensile and creep properties. However, the inclusions in P/M superalloy have an important impact on the safety and reliability of superalloy. By means of implanting SiO₂ inclusions artificially, the evolution rule of morphology, size and chemical composition of 30 and 60 μm inclusions in FGH96 superalloy during powder, hot isostatic pressing (HIP) and hot extrusion (HEX) processes was investigated by SEM, EPMA, TEM, nanoindentation and Micro-CT. The interfacial reaction mechanism between inclusions and matrix alloy was revealed deeply, the size change of inclusions during different stages was studied quantitatively, and the 3D morphology of inclusions was characterized. The results show that the inclusions in powder stage are long stripe or plate-like shape, the displacement reaction happened in the process of HIP, which produced the composite inclusions with TiO₂ inside and Al₂O₃ outside dispersed uniformly in the γ matrix, and the phase types of oxides were confirmed, furthermore, the reaction mechanism was figured out. Meanwhile, the denuded zone of γ' phase appeared around the inclusions with the dimension of 60 μm, but not 30 μm. The alloy matrix had higher elastic modulus and hardness than the denuded zone of γ' phase, implying that the denuded zone was softened zone. After the reaction, the dimension of inclusions became larger, the average size of 30 and 60 μm inclusions were 35 and 75 μm, respectively. During the HEX, owing to existence of the denuded zone, 60 μm inclusions had different deformation behaviors with 30 μm inclusions, and the dimension of inclusions obtained from statistics by SEM was used to contrast and validate with the results from formula calculation and Micro-CT.