Abstract: This article reasons the selection of ultrasonic phased array inspection technology for turbine welded diaphragm. How to determine the key process parameters is expounded and the designed process is applied to the inspection in manufacturing process of diaphragms of a 1000MW class power unit. The results show that ultrasonic phased array inspection process for welded diaphragm is reliable. The workpiece CAD loading function of workpiece loading system reduces the difficulty of defect signal recognition, improves the suitability and the detecting efficiency, which is worthy to be popularized.