Abstract: The high-temperature fatigue behavior and fatigue attenuation coefficient of 316 stainless steel welded components were systematically investigated from both material- and structural-level perspectives to address fatigue degradation under elevated temperatures. Low-cycle fatigue tests were performed at 450 ℃ on the base metal, weld metal, and welded joint specimens. The results indicated that within a total strain range of 0.5–1.0%, the welded joint exhibited the highest cyclic stress response, followed by the weld metal, while the base metal showed the lowest response. Based on the fatigue life differences between the base metal and welded joint, the ratio of total strain ranges at specific cycle numbers was determined, and a recommended fatigue strength attenuation coefficient for 316 stainless steel welded joints at 450 ℃ was proposed. By incorporating a combined kinematic hardening model and an improved damage model, the fatigue behavior of the welded joints was accurately predicted. Furthermore, a theoretical framework for evaluating the fatigue strength attenuation coefficient of welded structures was established, elucidating the influence of geometric characteristics on fatigue attenuation behavior.