Abstract: In this paper, the damping force response and energy dissipation of an electrorheological were been studied by applying sinusoidal signal．The results show that the electrorheological damping can be controlled by the electric field.　As the strength of electric field increased, the damping changed from linear to nonlinear and the dissipative energy increased. By analyzing the frequency spectrum of the response， it was found that the frequencies of harmonics are odd times of the fundamental frequency. As the strength of electric field increased, the shape of the hystersis loop of the energy dissipation changes from elliptical to rhombic, and the damping of electrorheological fluid is hystersis damping. 