Abstract: Design theories of a magnetorheolo gical fluid (MR fluid) damper based on the mixed mode of flow mode and shear mode were prese nted by using nonlinear Bingham plastic model.In the light of the technician requirements for Chang'an mini-automobile,a MR fluid damper was designed and fabricated by using commercial MR fluid.The nonlinear MR fluid damper model was validated experimentally.The results reveal that the design method is reasonable and the MR fluid damper for a specific application can be designed according to the design method developed in this paper.