A structure of an orifice plate for an engine mount filled with a magnetorheological (“MR”) fluid may include a core of which a center part may be formed at the center thereof and a blade part may be formed with a plurality of blades protruding in a radial direction from an outer periphery of the center part, and a coil assembly enclosing the outer periphery of the center part and wired up, wherein a gap may be formed between the blades so as to allow the MR fluid to flow between the blades and the coil assembly applied with current magnetizes adjacent blades to have different polarities.