The effect of vibration on the cohesive particle motion in the bed was examined by using discrete element method(DEM). The bed of dried fine particles was treated as the objective of calculation. The van der Waals force was used as the cohesive force because the van der Waals force was considered to be the main cohesive force in this case. Since the actual calculation time was too long, the fine cohesive particle was difficult to be treated. So a relatively large particle (1.0 mm in diameter) was used in calculation and the van der Waals force was assumed that the ratio of gravity force to van der Waals force of particle used in this calculation was equal to that of a fine particle (6.0 mu m in diameter), to express the effect of van der Waals force significantly. The calculation results were compared with that case of cohesionless particle. In the case with vibration, the cohesive particle motion in the bed is observed, though no fluidization state appears in the case without vibration, and there is no bubble in the bed even the fluidization state. In the case of cohesive particle, the collision energy between particle and wall caused by vibration gap propagates from the bottom to top of bed, and the particle moves vigorously at the top of bed in the case with vibration. As the vibration gap increases, the effect of vibration on the cohesive particle motion becomes larger, i.e., the low vibration frequency at the same vibration strength or the large vibration strength at the same vibration frequency promotes the fluidization of the bed. (c) 2005 Elsevier Ltd. All rights reserved.