Defects in the gas pipelines such as metal corrosion, pitting and cracking may destroy the pipeline’s integrity and therefore should be inspected regularly. Non-destructive testing based on the MFL-Pipeline Inspection Gauge (PIG) is usually performed for large diameter piping systems such as pipelines transporting crude oil or gas. In this technique, many factors can affect the MFL signal, but the magnetizer of the system is a fundamental issue that bears consideration. We present the results of research using finite element simulation (FEM) and experiments to optimize the configuration of a magnetization system for a 20-inch diameter PIG device. Factors to be investigated for optimization include the geometric dimensions of the magnetic yoke, the magnets, and the magnetic brushes with the goal on the one hand, ensuring the uniformity of the magnetic field distribution between the two magnetic poles, on the other hand, ensuring the generation of the MFL signal. The research results are used for the fabrication of PIG devices for use in the oil and gas industry.