Abstract: ASTM E2491—2008 provides the standard guide for evaluating performance characteristics of phased array ultrasonic testing instruments and systems. In this paper，we use the phased array technology to measure the beam focusing capability of phased array ultrasonic with wedge according with ASTM E2491—2008 so that we can identify the causes and effects of focusing capability in the factors such as the numbers of elements, the focal depth and the scanning angle. In the test, the block designed in ASTM E2491—2008 has been used, the elements used are 8, 16 and 32, and the focal depths used are 10, 50, 100, 150 and 200 mm, and the scanning angles are 35°, 45°, 60°and 70°.Through the test, we can find that a large proportion of the near field is in the wedge and only a small proportion of the near field is in the block. The smaller the scanning angle is, the larger the near field in the block is. And if the scanning angle increases, the focusing capability becomes weaker. The focusing capability is intensified when the number of the elements increases. The focal depth increases, the focal spot size increases, too. The resolution of the system will be better if the scanning angle is close to the physical angle of the wedge.