Abstract: In order to develop magnetic flux leakage (MFL) detector for submarine pipeline, magnetization effect on submarine pipeline is studied using onshore MFL detector. The finite element simulation software Ansys is used to analyze the effects of submarine thick wall pipe, concrete weighted coating and double-layered tube on leakage magnetic field. When a small-size flux leakage detector is used to detect submarine double-layered tube, the magnetic field strength of the tube wall can reach the lower threshold of required magnetic field of MFL testing, and therefore the detector needs to be improved. When a large-size flux leakage detector is used to detect submarine tube, the magnetic field strength of the tube wall can reach the requirements of MFL testing, and the quantification and identification accuracy of defect signals also can meet the design requirements of MFL detector. The research results are of great significance to guide the development of MFL detector for submarine pipelines.