Abstract : In the automotive field, semi-active suspensions based on magnetorheological (MR) fluid put forward a very interesting compromise between high performance and low power consumption. These devices have adjustable properties and damping parameter that can be controlled thereby optimize in real time their behavior over a wide frequency range of excitations. Under an external magnetic field, the MR fluids see their viscosity increases, with a response time lower than few milliseconds. In this dissertation, we present the design of a MR damper and an experimental test bench for a scaled-down semi-active suspension. The static and dynamic characterization of the damper is shown. Experimental evaluation of the damping force according to dynamic and electrical variables is presented and compared with the specifications used to assess the design method proposed. A Bingham model is proposed for the static behaviour of the damper whereas the dynamic behaviour is explained by a Bouc-Wen model. The last part of this study concerns the development and validation of several control and strategy laws for semi-active suspensions, in particular innovative laws based on model inversion EMR. A comparison performances study from comfort and power consumption point of view of each law is presented. Compared to existing control laws, these new control laws shown very interesting performances while reducing power consumption.