Abstract: In this paper, a portable phased array ultrasonic device was utilized to detect a 22.92 mm carbon fibre composite reference block, and theφ6 mm, φ9 mm and φ12 mm defects inside the block were scanned and imaged. It was proved that the TCG curves of different size defects from the same medium had the same varying trend and go to coincide. Three different imaging methods can determine the dimensions of defects accurately. Depending on the features of themselves, co-using these imaging methods can achieve the best detection and evaluation result.