Abstract: The multiaxial creep behavior and failure criteria of TP321 austenitic stainless steel were studied at 650 ℃. Firstly, typical multiaxial creep test types and their relevant domestic and international standards were reviewed, with particular emphasis on the advantages of notched bar specimens in simulating complex stress states. Multiaxial creep experiments were conducted using semi-circular notched specimens with different notch ratios (2.80 and 4.67), and the results were compared with those of uniaxial creep tests. Secondly, The bone point stress method was employed to characterize the multiaxial stress state, further obtaining the SHL form and Huddleston fracture failure criterion parameters, and fitting and evaluating the creep life of TP321 material. Finally, the finite element analysis of the stress evolution in the material cross-section was conducted by the K-R damage model, obtaining the corresponding fracture failure criterion parameters. Results show that TP321 material exhibits a significant notch strengthening effect under multiaxial loading conditions. The von Mises stress predominantly governs the creep rupture life of TP321 material, and the SHL criterion exhibits superior predictive accuracy in this study, demonstrating good potential for engineering applications and providing theoretical basis and methodological reference for the design and life assessment of TP321 high-temperature structure.