Abstract: Due to the heterogeneity of welding material and the coupling heterogeneity of probe caused by the heterogeneity of surface state, the biggest difficulty in eddy current testing of welding seam lies in the large local noise and low signal-to-noise ratio noise. In this paper, a special rotating probe and different types of detection devices are designed for eddy current detection of sealed welding between heat transfer pipe and tube-plate of steam generator in nuclear power plant, and a unique coil type selection and flexible structure design are designed to minimize noise and improve SNR. The testing technology has been systematically tested and the results of surface eddy current testing can be used to detect the sealing and welding surface and near-surface defects of steam generator heat transfer tubes and plates during service or manufacturing. The system and process can be widely used in eddy current testing of heat exchanger tube sheet seal welding in other industrial fields.