The mixing and segregation behavior of biomass particle have been investigated experimentally in fluidized bed made up of biomass-sand mixture with different biomass/sand ratios. The biomass is cylindrical-shape cotton stalk, and the sand belongs to the Geldart B category. The initial bed is thoroughly mixed and the gas superficial velocity varies to cover a wide range. The mixing and segregation behavior are analysed in terms of flow patterns, solid concentration profile and mixing index. It is found that as the gas superficial velocity gradually increases, the bed undergoes local segregation, global segregation, local mixing, global mixing and re-segregation. (c) 2008 Elsevier B.V. All rights reserved.