Abstract: In order to analyze the fatigue life of non-load-carrying T welded joints bearing longitudinal load, longitudinal structural stress and its constructing approach were proposed. Nodal loads normal to the weld section were converted to the distributive loads along the element edges. Analysis formula of membrane stress and bending stress was established by force balance theory. Equivalent plate thickness was proposed based on the base metal thickness and the weld height. Then the longitudinal structural stress at weld toe was calculated. The approach was verified by fatigue test for non-load-carrying T welded joints bearing longitudinal load. Results show that this approach has obvious advantages to analyze longitudinal loading welded structures,which can be employed to calculate fatigue life by revised equilibrium-equivalent formula, and the master S-N curve according to the theory previously proposed by Dong.