Abstract: When using magnetic flux leakage detection technology to detect the defect of boiler water wall tube, due to the influence of the fin structure of the water-cooled wall, the magnetic flux leakage signal strength at the defect location of the water-cooled wall tube will be weakened, leading to a decrease in detection sensitivity. In response to the above issues, the author of this article proposed an improved scheme of adding a magnetization unit to simultaneously magnetize the pipes on both sides of the water-cooled wall pipe to be inspected. Furthermore, the author conducted in-depth research on the feasibility of this scheme. A finite element model of the magnetization structure of the boiler water-cooled wall tube containing three magnetization units was established. The magnetic leakage signal strength at the defects of the water-cooled wall tube before and after adding magnetization units was compared and analyzed. Finally, the accuracy of the numerical calculation results and the feasibility of the improvement plan were verified through experiments. The research content of this article could provide reference for the development and application of magnetic leakage detection equipment for boiler water-cooled wall tubes.