<p>This paper investigates the ultimate load-carrying capacity of notched Ti₂AlNb alloy specimens at 550&#xa0;°C. Tensile tests were conducted on smooth and notched samples. To address the overprediction of ultimate load for notched specimens by models calibrated from smooth samples, an inverse optimization using notched round bar sample data was performed to refine the model parameters. The optimized constitutive model significantly improves prediction accuracy for both notched bar samples and four types of notched plates. A comparative assessment of the average stress method, local strain method, and large-deformation finite element analysis reveals that the latter, when integrated with the optimized model, provides the highest precision, with ultimate load errors below 4%. This validates the proposed method as an effective and applicable tool for engineering assessments of notched components.</p>