We have developed a prediction model of ultrasonic wave changes caused by microstructural changes in 304 stainless steel based on the theory of ultrasonic wave propagation and experimental results. The correlation between microstructure and ultrasonic waves was simulated in the model with microstructure components such as grain boundaries, voids, precipitates and dislocations taken into account. Material parameters used for the prediction model were determined from the literature, microscopic observations, and experimental results obtained from archive materials.Calculations were performed assuming respective and integrated changes of irradiation-induced microstructures and spectrum changes of ultrasonic signals due to microstructural changes were evaluated. Calculations for archive material were also performed for validation, and the results were reasonably consistent with experimental data. It was found that by selecting appropriate indicators one can identify the nature of microstructures and quantify the microstructural changes due to irradiation.© 2013 ASME