Abstract: Ultrasonic phased array focusing ultrasonic energy on the inspected area to make the test results more obvious. The focus depth setting had great influence in defect quantification. This paper had detected the Φ2mm drill holes of different depth like 4,9,13,18,23,29,35 mm by using ultrasonic phased array scanning technology. As per the test result, when focus depth setting equal to the hole depth, the tolerance of the hole depth and the hole aperture will be 迷你 mum. When the focusing zone in which ultrasonic beam energy concentrated is approximately 5mm front and after the focusing point setted, and the detecting and sizing the defect has better accuracy. The deviation could be controlled in the range of 1mm.