Abstract: The joint of FGH96/GH4169 super alloy was obtained with changing pressure on an inertia friction welding machine and the welded joint temperature was measured. After welding, optical microscope, scanning electron microscope(SEM), electron microprobe analysis (EMPA) and tensile testing machine were used to investigate the microstructures, mechanical properties and fracture morphology of the joint . The results showed that the temperature around the interface exceeded above 1 100 ℃. The microstructure in the weld zone (WZ) consisted of refined and equiaxed grains and that in the thermo-mechanically affected zone (TMAZ) consisted of deformed grains. After welding γ″, γ′ was dissolved partly in TMAZ and completely in WZ. The sizes of the refined grains became smaller with increasing pressure. Elemental diffusion layers existed on the interface and the layers became wider with increasing pressure. The results of tensile properties showed that the transverse tensile strength rose with pressure, and tensile specimens fractured at the TMAZ of GH4169 side. Micrographs confirmed that the fracture was the mode of ductile fracture.