However three-body vibrating screen is widely used in engineering practice, many dynamics of it have not well been addressed. For studying three-body vibrating screen dynamics, the vibrating screen dynamic model and the virtual model were established. Through deriving the dynamic equations and simulating the vibrating screen start - running process, the analytical equations and the trajectories were obtained. Studies have shown that the VBVS vibration in the Z direction is complex and the X direction which perpendicular to the axis of exciters is the sensitive direction for the installation error. In addition, the SBD’s trajectories in the direction which does not exist exciting force are superimposed by the trajectories of USB and LSB.