Abstract: Ultrasonic CT is a nondestructive detection method which use elastic wave propagation time of ultrasound in the test object to reconstruction of velocity distribution.Through the use of special equipment to record propagation time from a source to a receiving probe of ultrasonic wave,and then the velocity calculation,inversion,by analyzing the software analysis distribution characteristics of the acoustic propagation velocity within component indirect access component strength and internal uniformity and other information.This method was applied practically in large concrete member in nondestructive testing.Comparing with other test measures,ultrasonic CT testing technique with high efficiency,accuracy and direct test results.The method can detect not only component defect,combined with uniaxial compressive strength of concrete sampls for batch production,also can strength of the component evaluation,so that it is first method of choice for large concrete defect survey.