Fluidized beds are widely employed in industrial operation due to their excellent solid mixing, heat and mass transfer properties. Deeper knowledge of the fluidized bed hydrodynamics would provide the base for development of a fully predictive model. This study highlights the model development for hydrodynamic study and the effect of particle size to the solid fluidization in fluidized bed gasifier using Eulerian-Eulerian multiphase model coupled with kinetic granular theory in CFD software, Ansys Fluent v6.3. The result obtained has been compared with literature data and had proven that the model is capable of accurately model the hydrodynamic of fluidized bed gasifier. Different particle size will give different hydrodynamic flow in the gasifier and particle size in the range of 250-300 urn is observed to give the best solid fluidization behavior in the gasifier. This model can be used further to study the effect of other parameters such as steam inlet velocity and solid initial bed height on the hydrodynamic of the fluidized bed reactor. © 2011 Asian Network for Scientific Information.