Uniaxial hot compression deformation experiments for a new type nickel-based powder metallurgy (P/M) superalloy FGH98 I have been performed on Gleeble-1500 thermal simulator, and the hot deformation behavior has been investigated under the conditions of deformation temperatures of 950-1150 oC and strain rates of 0.0003-1 s-1. The strain rate sensitivity m maps and the power dissipation efficiency η maps have been established and compared at different strains. The microstructural validation of processing maps also has been done. The results show that the flow stress decreases with the deformation temperature increasing and strain rate decreasing. The maps of m and η are similar at different strains, and the values of m and η in the peak zones gradually increase with the strain increasing. When the true strain is 0.5, the alloy has peak η of 40% and peak m of 25% at 1050 oC and 0.0003 s-1, which corresponds to dynamic recrystallization and grain refinement without inner cracks. The above results can be used as a theoretical reference for the optimization of actual hot working processing of FGH98 I alloy.