Abstract: Electrorheological Fluid (ERF) is a kind of novel intelligent material with adjustable physical parameters under the action of an applied electric field. By applying different electrical voltages, the storage modulus, loss modulus and loss angle of ERF change simultaneously. In this paper an acoustic impedance measuring system based on ultrasonic (shear) wave reflection method is designed to measure such changes of ERF parameters. Furthermore, the relationships between viscoelastic parameters obtained by acoustical impedance and electrical field intensity can be determined and analyzed so as to realize accurate control for ERF. In addition, the processing technology involved with electrode insulation is tested to explain its influence on measuring acoustic impedance and loss modulus of ERF.