Supercritical water (SCW) fluidized bed is a new and promising reactor for gasification of wet biomass. In this paper, the particle distribution and fluid hydrodynamic characteristics in SCW fluidized bed were studied comprehensively by the discrete element method (DEM). The results from DEM simulation show that there exists a non-bubbling fluidization when superficial velocity is in the range of minimum fluidization velocity and minimum bubbling velocity although the particles are categorized as Geldart B. Particle circulation, including internal circulation and gross circulation are responsible for solids mixing in SCW fluidized bed. Particle circulation in SCW fluidized bed is not only induced by bubble motion, but also influenced by the vortices in bubbles. Other characteristics such as voidage distribution, particle and fluid velocity, granular temperature, and particle Reynolds number in SCW fluidized bed, are also discussed. (C) 2014 Elsevier Ltd. All rights reserved.