Inertia friction welding (IFW) was conducted on FGH96 superalloy which is commonly used in the aviation engine rotor. After welding, the joints experienced solution treatment and aging-treated. The morphology, internal residual stress and distribution characteristics of joints were measured and analyzed at different solution treatments by the contour method. Then the influence of solid solution treatment temperature on the residual stress was studied. The results show that the width of the welding zone is narrow at the center and wide on both sides. With the increasing of the solution treatment temperature, the welding line becomes blurred and the grain grows significantly. The circumferential residual stress peak at the welding center reaches 1076 MPa. Then the residual stress along the axis direction becomes compressive, and the circumferential residual stress in the inner surface is greater than that of the outer surface. After heat treatment, the tensile circumferential residual stress inside of the whole specimen is significantly reduced to −250–250 MPa, but the asymmetric distribution trend of the circumferential residual stress is consistent with that of no heat treatment.