It is of great significance to establish an in-situ settlement monitoring system for the magnetorheological (MR) fluid in devices. By studying the relationship between the concentration gradient of MR fluid and the dielectric constant of the sediment, the monitoring method and system based on an open-plate capacitor is designed. The influence of center pillar height on the electric field distribution is simulated, and the in-situ monitoring of MR fluid show that the system can effectively measure the static settlement of magnetorheological fluid, the dielectric constant of the sediment increases with the heightened concentration, and the sedimentation ratio lowers with the development of the settling process.