Abstract: In view of the characteristics of eddy current testing of fillet welds in tube sheets, the relevant factors affecting the implementation of conventional eddy current testing (including shape, material, etc.) are investigated. On this basis, the ANSYS finite element simulation technology is used to optimize the design of the special sensor. The permanent magnet is added, and the signal processing method of restraining the end effect of eddy current testing is adopted, thereby reducing the range of the end detection dead zone and improving the detection accuracy of weld defects. The simulation and experimental results showed that it could realize those deep defects detection in the fillet weld of thin-walled tubes plate when magnetization was applied to the pipe wall and differential processing means was undertaken for the detection signals, proving the feasibility of eddy current testing for the tube plate welding structure and improving the detection efficiency.