Abstract: The Vickers hardness,microstructures and properties of GH4169 are very sensitive to heat-processing techniques.Coarsening and mixed grains will appear when mistechniques are choosen.It increases the stress rupture sensitivity and decreases the impact toughness.It was found that superalloy GH4169 inertia friction pipe joint has superfine grain and fine grain distributing along the axial direction by the research experiment conditions.This phenomenon was analyzed according to the dynamic recrystallization property of superalloy GH4169 and the unique thermo deformation condition in inertia friction process.The result shows that the temperature,strain and strain rates of superalloy GH4169 are the main reasons to cause the fine and superfine grain microstructure.Hot deformation dynamic recrystallization process is very rough and sufficient in the weld region of GH4169 inertia friction pipe joint,and the microstructure shows fine and homogenous equiaxed grains.There is no coarsening and mixed grains been found,although the grains are not homogenous in the whole joint.