FGH96 is the second generation of power metallurgy superalloy in China, it is very difficult to forge and form by the conventional forging process. Therefore, in order to explore a reasonable preparation method for fine-grained disc billet, the hot die forging experiments were carried out at hot die temperature of 900 ℃ with different strain rates, deformation temperatures and deformation amounts to study the change rules of microstructure for power metallurgy superalloy (P/M superalloy)FGH96. The results show that when the forging temperature is lower than γ′ phase solid solution temperature，the microstructure becomes more uniform with the increasing of the deformation temperature, and when the deformation temperature exceeds the γ′ phase solution temperature, there is a tendency of grain growth. In addition, the grain sizes of alloy are refined with the increasing of the deformation amount, and the microstructure is not uniform when the deformation amount is low, but the better refined structure can be obtained when the deformation amount exceeds 30%. When forging with a large deformation amount greater than 30% at the deformation temperature range of 1050-1130 ℃, the grain sizes can be increased by more than three grades, and the recrystallization structure about grade 12 can be obtained by the large deformation upsetting and repeated upsetting and drawing, which significantly increases the tensile strength and presents the fracture characteristics of intergranular and transgranular mixed fracture.