Abstract: Filler cleaning is a challenge that affects the efficient separation of FCCS particles by electrostatic methods and limits the utilization of the oil slurry. Two filler cleaning methods are proposed in this paper, the flushing desorption method and the electrostatic desorption method, where desorption is achieved by respectively applying a flow field or an electric field to the fillers immersed in a cleaning solution (ethyl acetate). Also, the “rough particle-smooth plane” contact model between particles and filler was established, and the particle force model was established by analyzing the movement of particles in the process of cleaning. Furthermore, combining the established contact model and force model, the detachment model of particles was proposed. In this model, the dimensionless number λ is used to discriminate the attachment state of particles whose validity was verified by experiments. The experimental results showed that the cleaning efficiency of flushing desorption method and electrostatic desorption method increase with the increase of flow rate and voltage, which reached 50.5% and 61.4% at 0.1m/s and 14 kV.