Abstract: The joint between the safe-end of the reactor pressure vessel and the main pipe is the same kind of steel weldof austenitic stainless steel. The conventional ultrasonic inspection is difficult to cope with the task due to coarse grain. Combining the characteristics of welded structure and the advantages of phased array detection, a technical scheme for phased array ultrasonic inspection of the same kind of steel weld is proposed, and the parameter design method of phased array probe is described. The parameters determined by the technical scheme are simulated by the sound field and verified by the actual test. Finally, the comparison test between the reference test block and the conventional probe is carried out. The test results show that the designed phased array detection technology can effectively test the same kind of weld on the safe-end of the nozzle. Its detection ability is higher than that of conventional ultrasonic testing technology, and it can effectively reduce the number of probes and inspection time.