Abstract: Based on the study of the turbo disk and the compressor disk of high-quality aero engine,systematical analyses and calculation of the IN-718 superalloy simulated workpieces were carried out in this paper.The energy method is used to predict the behavior of IN-718 tubular specimens with an outside diameter of 11.5 mm and inside diameter of 7.5 mm during the friction welding and the closed form solution is presented for temperatures developed during heating in weld piece of finite.So theoretical equations of thermo mechanical parameters can be easily got from the energy model.With the equations,curves of separating radius and instantaneous temperatures on different conditions are found.As result of it,the cause of cracks in the jointing of the welding zone is shown.As shown in this paper,the result can be used to lay down thermo-mechanical parameters scientifically and improve deformability of IN-718 supperalloy in friction welding.