Abstract: The bottom seal head and the pipe plate circumferential weld of the steam generator in EPR project is the important boundary of the first loop. Because of the large thickness and the spherical shape of the weld, the ultrasonic inspection process should be made with full consideration of the effects such as the attenuation of the probe sound beam and the change of the angle of the probe, so as to meet the requirements of relevant inspection standards. With the in-depth study of the RCC-M and EN 1713 standards, conclusions can be made based on the analysis and simulation of the energy and angle change of the probe, that, by adding a 60 degree probe in the inspection process, the requirements of standard can be satisfied, and the risk of missing dangerous defects can be reduced so that the quality of nuclear safety equipment can be ensured.