Abstract: In order to predict the changes in magnetically fluidized bed from aggregate fluidization to par-ticulate fluidizaion, or vice versa, the criteria of magnetically stabilized fluidized bed are formulated, which are different from Rosensweig s criteria and avoid some difficulties from Rosensweig s method. The criteria are based on Foscolo s "particle bed model", which is derived from a fluid dynamic mechanism for particle - particle force transmission and hypothesizes particles chained with each other in the fluidized bed. This hypothesis is very well adapted to particles in magnetically fluidized bed. By following Foscolos model and considering magnetic field on particles, the criteria can describe the stability of magnetically fluidized bed. The stability diagrams from the criteria agree with Cocker s experimental data. The results prove that Foscolo s "particle bed model" is also applicable magnetically fluidized bed. According to the criteria, the effect of magnetic field is analysed on the stability of magnetically fluidized bed in both the laminar and turbulent flow regime. Comparing the criteria we proposed with Fos-coles criteria of fluidized bed, we fined that magnetic field is conducive to increasing the stability of magnetically fluidized bed.