Abstract: In order to improve the fatigue load carrying capacity and efficiently predict the fatigue failure position of heterogeneous joint, the influences of groove angle and difference between welded materials on joint stress concentration factor are studied based on finite element method. The weld root stress concentration factor and weld toe stress concentration factor relation equations of flat heterogeneous butt joint are also developed.The result shows that weld root stress concentration factor increases with the increase of groove angle and difference between welded materials, weld toe stress concentration factor decreases with the increase of groove angle and difference between welded materials. The results calculated by stress concentration factor relation equations are in good agreement with the finite element method results, and the relative error is less than 3%.