Abstract: In order to realize the lightweight design of the magnetizer, a method based on the composite magnetization of permanent magnet and electromagnet was proposed to optimize the design of the magnetizer and its structure. With comparison and analysis of various magnetization schemes combined with finite element method,the results show that the permanent magnet and electromagnet have the characteristics of small size, light weight and simple structure. The structural parameters are further optimized and shown to meet magnetic flux leakage detection requirements for defects such as oil well pipe through holes and inner blind holes, so as to verify the magnetization ability of the composite magnetizer. Compared with the through-coil magnetizer, the mass of the compound magnetizer is reduced by more than 50%, which is more conducive to the carrying and operation of the instrument. Compared with the permanent magnet magnetizer, the suction force while disassembling the magnetizer is small, which is more convenient for operation.