Magnetic-valve controllable reactor (MCR) has become many researcher’s topic of the day because of its versatile use in power systems. MCR utilizes the concept of magnetic saturation to control power flows in the power grid. It is as simple to operate and maintain, and reliable as an ordinary transformer. However, magnetic-valve controllable reactor works under a more variety of complex excitation condition because of the superposition action of AC and DC excitations. This paper carefully discusses the distribution of magnetic field of MCR core, provides an understanding of the range of inductance adjustments and further analyzes the working current waveform. Based on that, the finite element analysis software ANSYS Maxwell is used to design and examine a 3-D prototype model under different control voltage levels. The method of transient solution is applied for the reason being that it simultaneously has both AC and DC voltages. The AC voltage is kept constant while the DC voltage is varied from the minimum to the maximum rated value. The simulation results confirm that the magnetic-valve controllable reactor works in the saturation region of the magnetization curve under the combined excitation of AC and DC. The inductance adjustment range shows that the MCR inductance value can be smoothly and continuously varied. In addition, the working output current contains little odd-order harmonics that can be mitigated if filtering device is used or the magnetic valves are designed carefully. By observing the simulation results and analysis, one can gain a thorough understanding of MCR under actual working condition. It provides a reliable basis for the performance design of magnetic-valve controllable reactor.