Transient behaviors of (ER) fluids in tensile flow and applied stepwise voltages were experimentally studied. The transient tensile stress rises exponentially with time. The characteristic rising time of tensile stress is independent of the amplitude of the applied voltage and the tensile velocity, while the amplitude of tensile yield stress is significantly affected by the two factors. The transient tension applied as a stepwise voltage is different from a stable tension pre-applied at constant voltage in different particle chain structure forming processes. Because of the chain aggregation during an intermittent voltage on–off test, the achieved tensile yield stress showed an exponent of 2.75 to the applied electric field at low separation velocities (0.2  mm s⁻¹), higher than the square relationship predicted by traditional polarization models, and the exponent of 1.5 predicted by the conduction model. The results achieved in this study show that the mechanical properties of ER fluids are greatly affected by the method of applying the electric field, the strain rate, and the gap geometry between electrodes. These factors should be properly considered in the design and control of ER actuators.