The invention relates to modified electrodes for ER fluids prepared by adding a rough, wear-resisting, and low conductive modified layer on the surface of metallic electrodes. The material for the modified layer can be at least one from diamond, alumina, titanium dioxide, carborundum, titanium nitride, nylon, polytetrafluoroethylene, adhesive, and adhesive film. Through the addition of the modified layer, the adhesion of the ER fluid to electrodes is increased so that the shear stress measured near the plates is close to the intrinsic value, which makes the ER fluid applicable, while reducing the leakage current and increasing the breakdown voltage of the ER fluid equipment.