Abstract: The high frequency ultrasonic test of using direct contact method to SUS306 stainless steel samples,which were treated by high temperature heat treatment and stretch experiment,is described in this paper.The ultrasonic attenuation coefficient,average grain diameter and elongation at breaking of the sample being tested are obtained through echo analysis.The relationships between average grain diameter,elongation at breaking and ultrasonic attenuation coefficient of samples are also established.These results are expected to be useful for early assessment of material thermal fatigue damage advance.