To date the standing surface acoustic wave (SSAW) could manipulate particle meeting various demands, based on particle size, density and shape. However, particle scale information is not easy to be studied by experimental method and conventional continuum method. In this paper, the particles are described by discrete element method (DEM), the fluid is simulated by computational fluid dynamics (CFD). The acoustic force acted on each partide is implanted based on Gor'kov theory. The established model is validated as the particle flow pattern together with the focusing length and width agree well between simulations and experiments. Further simulations reveal more particle scale information at length. The particle focusing process can be catalogued into three regions, which are strongly influenced by particle and acoustic properties. The particle collides' effects are not significant as drag and acoustic force, but irreplaceable on the subsequent particle rotation in ordering the particle pattern in focused layer. (C) 2019 Elsevier B.V. All rights reserved.