Most of machines and structures are often used recently in severe environments. It is necessary for prediction of failure and remaining life of them to evaluate damage of material with use. For in-process and in-service damage evaluation of structural materials, nondestructive methods for material property determination are required. Round bar tension test, Charpy V impact test and static 3-point bending test as well as ultrasonic attenuation and wave velocity measurements are made by using mild steel plate prestrained under various conditions. Those tests are carried out for the purpose of establishing the nondestructive methods for material property characterization. Correlations between results of material tests and ultrasonic attenuation or wave velocity are examined. In the plate prestrained up to the plastic region, strength increases and ductility decreases with increasing degree of prestrain. Notch toughness decreases with increasing degree of prestrain. Relationships between mechanical properties and ultrasonic attenuation or wave velocity, in plate prestrained up to the plastic region, are represented approximately by straight lines or smooth curves. Strength decreases with increasing attenuation coefficient and with increasing wave velocity. Ductility increases with increasing attenuation coefficient and with increasing wave velocity. Notch toughness increases with increasing attenuation coefficient and increasing wave velocity. Using the results above mentioned, mechanical properties of prestrained steel such as strength, elongation and notch toughness can be estimated nondestructively from ultrasonic attenuation or wave velocity.