An idea of spatial vibrating screen was presented to meet the different needs in screening crops，and its main body has been designed. A kind of four degrees-of-freedom parallel mechanism has been used by the screen as the main body. It could adjust the amplitude and the vibration direction of the vibrating screen conveniently. This parallel mechanism included four legs，where two legs were types of R-R-P，the others were R-R-R-R-P. The moving platform of this mechanism，used as a screen platform，could achieve a movement in two durations and a rotation around two directional axes. The kinematics modeling method of this mechanism was studied by using conversion matrix, and the kinematics positive and inverse solutions of this mechanism were presented. The result indicated that this mechanism could be applied in the vibrating screen.