We investigated an operating characteristic of linear-type magnetic flux pump (LTMFP) as a current compensator under the various conditions. In order to explain the mechanism of the LTMFP, the magnetic behavior of superconducting Nb foil according to pumping actions should be understood. In this paper, the magnetic field analysis of superconducting Nb foil installed in LTMFP has been performed based on the three-dimensional finite element method (3D FEM). Through the simulation analysis, the normal spot region on the superconducting Nb foil is found to be enhanced swiftly over about 20 Hz. The simulated finding agreed with an analytical estimation based on the phenomenon of magnetic diffusion.