Abstract: The current main specifications do not include requirements for the detection method and quality level of ferritic thin-wall butt welds (wall thickness 3~6 mm). This article starts from the phased array detection principle and uses sound beam simulation to analyze its detection process, The sound field simulation and analysis of phased array probe parameters are used to summarize the phased array detection process of ferrite thin-wall butt welds. The designed phased array probe and process are used to measure the simulated specimens containing a large number of natural defects. At the same time, the sound field simulation is used to calculate the simulated specimen defects, and the results of the two methods are compared, so as to conclude that the ferrite thin-wall welding acceptance criteria for seams.