The mechanical properties of FGH96 superalloy after long-term aging were studied with tensile tests, stress rupture tests, and creep tests. The microstructure and precipitation phases were investigated by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Results show that at the condition of aging temperature of 550 ℃ and 650 ℃, aging time from 100 h to 7 500 h, the grain size, morphology of γ' phase, fraction of MC plus M₃B₂ phases, tensile properties, and rupture strength of the FGH96 superalloy after long-term aging keep nearly the same with those before long-term aging. The factions of γ' phase and Cr₂₃C₆ phase increase with increasing aging time at 650 ℃ while they remain almost unchanged at 550 ℃, which leads to the increasing residual strain of creep deformation for the 650 ℃ aged FGH96 superalloy.