Abstract: To improve the reliability of the carbody structure and reduce the rework cost, a method for analyzing the strength of fillet welds taking both theory and engineering practice into account was proposed by drawing on the carbody design experience from the “In-depth Research Project on Lightweight High-strength Stainless Steel Carbody Technology”. Namely, FEA was conducted in two stages. In the first stage, FEA using shell elements was adopted. If the stress of a node regarded as a fillet weld under the static strength condition exceeded 0.3 times the allowable stress at this stage, the submodel method was used for the secondary static strength verification. If the directional stress fluctuation range of a node regarded as a fillet weld under the fatigue condition exceeded 0.3 times the allowable directional stress fluctuation range at this stage, the submodel method was used for the secondary fatigue verification. The submodel was required to reflect the true geometry of the solid fillet weld according to the weld symbols on the drawing. The practice of multiple export projects indicates that the coefficient of 0.3 is set reasonably. This method not only identifies the over-stress points undiscovered by conventional methods, but also has no significant impact on the design efficiency.