A new soil-tuber separation device on potato harvesters has been developed. It mainly comprises a linear motor, a rectangular screen, a frame, four supporting springs and four dampers. It is the first time to propose that the soil-tuber separation device is driven by the linear motor. Forces acting on the rectangular screen are found. A differential equation for describing the forces is set up. An equation for evaluating exciting force of the linear motor has been derived from the solution to the differential equation. An equation of the factors affecting on the device resonance has also been obtained. Additionally, an equation for evaluating the deformed magnitude of the damping springs in the dampers has been derived. And finally a motion simulation experiment for the rectangular screen on a potato harvester has been done with the Matlab/Simulink module. The experiment expressed that the method is feasible.