Abstract: In this paper, for the purpose of evaluating the fatigue life of the loader’s front frame, three typical welded joints are extracted from the key parts of the welded structure of the front frame, and the fatigue test and analysis are carried out. Based on the local strain energy density method, the fatigue life curve is obtained through the experimental data, the accuracy and applicability of the theory are then verified by the fatigue data of the cross joint in the literature. The results show that the local strain energy density method can be used for the fatigue assessment of weld root and weld toe failure. Fatigue cracks at different positions will affect the rigidity of the structure, and thus the fatigue life of the structure. The influence of the size of the weld foot and the penetration depth of the joint on the fatigue life of the welded joint is studied, then derived the fatigue failure position transition interval from the local strain energy density method. The accuracy of the transition interval between weld toe failure and the root failure was verified by the fatigue data in the literature, which provides a basis for the fatigue design of partial penetration T-joints.