Abstract: The safety weld of steam generator is located in the SG(steam generator) room, and it is an area of high dose level. The pipeline has a major diameter and thick tube skin, and it is made by cast. So it is hard to inspect it with other NDT methods, such as ultrasound. Radiation inspection was chosed to detect the weld, it need only to place the radioactive source in the right position, then the inspector can leave. When the exposure is ended, the inspector can go into the SG room and take out the film. During the process, the inspectors don’t need to stay in the room too long, and the quality of the weld could be evaluated through the film, so it is more adaptive than ultrasound. The article describes the main points of inspecting the safety weld with RT method, it is proved the correctness and reliability by the practice in the Ling Ao Nuclear Power Station, and the improved methods and views for the testing in service was expressed at last.