In order to reduce the effect of reduction of the magnetron energy dissipation capacity of the magneto? rheological damper under a micro-amplitude，medium and high frequency excitation，this paper proposes a method to increase the working pressure by increasing the initial working pressure of the magnetorheological fluid in order to improve the magnetorheological damper energy dissipation capability under a medium and high frequency excitation. Based on compressible characteristics of magnetorheological fluids，a mechanical model of magnetorheological damper was constructed. The effect of working pressure on the damping force at medium and high frequency excitation was analyzed. A single rod linear liquid spring-type magnetorheological damper without a compensation device was designed and processed，and the accuracy of the mechanical model was verified through experimental tests. The experimental results under sinusoidal excitation showed that：increasing the working pressure of the magnetorheologi? cal damper can make the damping curve much fuller. When the working pressure is higher，the energy consumption capacity of the magnetorheological damper is significantly better than that of the magnetorheological damper when the working pressure is lower. According to the experimental results，it is also found that compared with the initial pressure of standard atmospheric pressure，when the initial pressure is 5 MPa，the maximum damping is increased up to 31.3%. The maximum increase in energy consumption is 78.5%. In addition，by increasing the working pres? sure，the magnetic field in the working area is more likely to saturate. The equivalent stiffness and equivalent damp? ing coefficient are increased with the increase of the working pressure.