Polar molecule dominated electrorheological (ER) fluid is a new type of ER material with high shear stress. The alignment of polar molecules adsorbed on the dielectric particles in the direction of the high local field between the particles plays a decisive role in such new ER fluids. In measuring the current density of ER fluid composed of Ca—Ti—O particles, it was found that the conductive behavior of the fluid exhibits Poole-Frenkel character, which is one of the particular features for polar molecule dominated electrorheological fluids. By heating the Ca—Ti—O particles at 500 ℃ to remove the polar molecules adsorbed on the particles, however, the current density of ER fluid fabricated with pure Ca—Ti—O particles has linear dependence on the electric field approximately, same as in the traditional ER fluids.