Abstract: Numerical simulation method was used to analyze the welding residual stress of low strength match butt joint under the condition of two constraint conditions and five yield strength match factors.The results show that the three-way residual tensile stress of low strength match joints at the weld root is small and has little influence on static load strength.The three-way residual tensile stress at the weld toe is large and has adverse influence on fatigue strength and cold crack performance.When yield strength of weld metal decrease every 25MPa,the longitudinal residual stress of free state and transversal residual stress of constrained state will reduce by about 11MPa.