Abstract: The shakedown behavior of U-groove butt welded joints under cycle thermo-mechanical loadings was studied by ABAQUS according to the nonlinear superstition method.The effect of the geometrical scale of welding line,yield stress,thermal expansion coefficient and Young's modulus of the base material and weld material as well as the thickness of piping on the shakedown behavior were studied.Results showed that the geometry of welding line has little influence on the shakedown region, while the difference between the yield stress,thermal expansion coefficient and Young's modulus of the base material and welding material influence the shakedown behavior significantly due to the great local stress.Lastly,the shakedown estimation method of U groove butt welded joints was developed for engineering designs.