With the characteristics of compact structure, reasonable layout, compact size, light weight and easy to carry, this kind of detector can be directly pl ed into AC, as well as be equipped with AC magnetized power supply (AC battery pack) and DC magnetized power supply (DC battery pack), which is of high efficiency and compactness. Besides, it is applicable for inspection of hull welds, high-altitude steel structure welds and internal operation of pressure vessels. Moreover, it is suitable for magnetic powder inspection of surface and near surface defects for various steel structures, boilers, pressure vessels, pressure pipes and welding structures in electric power, metallurgy, petrochemical, machinery and other industries.