Supercritical water (SCW) fluidized bed is a novel biomass gasification reactor which uses SCW as fluidized medium and non-spherical particles as bed materials. In this paper, a new non-spherical particle drag model was developed for the sphericity between 0.6 and 1. The drag model was applied to simulate the two phase flow in the SCW fluidized bed. We also conducted an experimental study to verify the model. The simulated results of bed expansions agree well with experimentally measured data in the ambient, sub-critical and supercritical zones. With increasing superficial velocity, a transformation from homogeneous to the bubbling fluidization mode in the SCW fluidized bed with Geldart-B particles was observed by the numerical simulation. The fluidization regime of the SCW fluidized bed evolved from a pseudo-homogeneous expansion to heterogeneous expansion with an increasing temperature, which can be viewed as an intermediate fluidization between the classically bubbling and homogeneous fluidization. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.