Abstract: Coil magnetization is the most widely used magnetizing method. The basic characters of coil magnetization were analyzed , and the influence of the geometric size of coil, number of ampers turns and magnetic flux gathering plate on magnetizability was studied by using the finite element method(FEM). Magnetizability of different method of magnetization were compared and analyzed, and the distribution of magnetic lines of the pipeline were computed. The relationship between magnetic field strength, lift-off and tangential component of the magnetic leakage flux density was studied. And a detail description of effectivity and significance of magnetic flux gathering technique was given. The analytical result provides a very important foundation for the design of coil magnetization.