Abstract: Fluidization and organic matter degradation of bioparticle play important roles in enhancing the efficiency and stability of the biological fluidized bed reactor. In this paper, some behavior characteristics, such as particle streamline, particle mixing, particle cluster, bioparticle granulation, bioparticle absorption and oxidation of organic matter and bioparticle mass transfer-reaction, are discussed. This paper also suggests that some measures can be adopted to strengthen bioparticle behavior by choosing support correctly, setting reactor internals reasonably or applying immobilized cell technique and so on.