We studied microstructure changes of 304-type austenitic stainless steel subjected to a tensile stress at . We monitored the shear-wave attenuation and velocity using electromagnetic acoustic resonance (EMAR). The attenuation peaks at 40% to 50% and a minimum value at 70% of the creep life, being independent of the applied stress. A drastic change in dislocation mobility and arrangement interrupted this novel attenuation phenomenon, as supported by SEM and TEM observations. The relationship between attenuation change and microstructure evolution can be explained with the string’s model. EMAR demonstrates a potential for assessing damage advance and predicting the remaining creep life of metals.