Flux pumps are the kind of devices that can magnetize closed superconducting magnets in a gradual manner. High-Tc Superconducting (HTS) flux pumps are particularly promising for high field applications, due to the fact that lossless HTS coils are unavailable. The physics of these devices is also attractive. In this paper, we propose a modeling methodology for a transformer-rectifier HTS flux pump switched by dynamic resistance. A finite element model is built in Comsol and solved by 2D H-formulation. The simulation result is verified by experimental data. The simulation will give a clear picture of how flux pumping occurs in the superconductor. It will show flux motion across a superconductor by shifting the electric central line, which is a unique nature of type-II superconductors. This work may be interesting in the understanding of magnetization of High-Tc Superconductors.