Abstract: The fractional-order model for testing system of magnetorheological fluid was built up and used to make simulation, a self-made rheometer was used for loading sine wave currents on different magnetorheological fluids. The results show that the computational data in the fractional-order model could fit the experimental data well, and the viscoelasticity of magnetorheological fluid could be got from the model parameters and the fractional-order system model could describe the damping characteristics of magnetorheological fluid from systematic viewpoint.