The swing-bar sieve is a separation machine that is widely used in grain grading and cleaning as well as seed processing. The motion of the screen deck is a complex planar motion. In this paper, the LA-LK laboratory scale swing-bar sieve and soybean particles are taken as the research objects. The real-virtual boundary method is proposed to build the geometrical model of the screen deck. The motion of the screen deck is modelled using the planar multibody kinematics. The flowing and passing of soybean particles on the screen deck are simulated by the coupled model of the discrete element method (DEM) with multibody kinematics (MBK). In addition, experiments using the LA-LK swing-bar sieve are conducted. The simulated results are in good agreement with those obtained experimentally in terms of the distributions of passing percentage for different size ranges of soybean particles along the screen deck. This verifies the real-virtual boundary method and the coupled model of DEM with MBK we proposed in this paper. This work provides a reference for the design optimization of the swing-bar sieve and the related research. (C) 2019 Elsevier B.V. All rights reserved.