Magnetorheological elastomer (MRE) isolators are semi-active seismic restrained devices that utilised elastomeric materials to produce controllable stiffness. The existing passive conventional isolator is not efficient in various ground motions, while the laminated MRE isolator is only flexible horizontally. An innovative new concept of the MRE isolator differs from that of the laminated steel-rubber layered isolator presented in this research. The study focuses on a new MRE isolator designed by adopting the engine mounting concept based on the electromagnetic circuit simulation studies. The proposed MRE isolator design relies on an optimised magnetic field passing through the MRE, which is aimed to obtain adjustable stiffness. The Finite Element Method Magnetics (FEMM) has been used to simulate the electromagnetic circuit to generate magnetic fluxes that penetrate through the MRE effective area. The principal design parameters approaches have been analytically determined by considering the selection of materials, the diameters and lengths of shafts, the shape of the MRE mounts, and the thickness of the housing.