Abstract: To study the local bearing stability of friction stir welded (FSW) 6061-T6 aluminum alloy I-section beams, local pressure-bearing tests were conducted on six FSW aluminum alloy I-beams. Analyzed were material mechanical properties, initial geometric imperfections, welding residual stress distribution, failure modes, and local bearing capacity. A validated finite element model was used to perform a systematic parametric study. Parameters included web height-to-width ratio, loading length, flange and web thickness ratios, and weld number and width. Research results show that Eurocode EN 1999-1-1: 2023 gives conservative predictions. The local bearing capacity is underestimated by 89% for non-welded specimens, by 49% for single-weld specimens, and by 17% for double-weld specimens. The calculated results also show large scatter. A modified formula based on EN 1999-1-1: 2023 can significantly improve the prediction accuracy for both welded and non-welded 6061-T6 aluminum alloy I-beams, and the scatter of its calculated results is clearly reduced.