Abstract: This paper analyzes the physical properties of dense medium solids, and concluded that particle size distribution is main factor that affects fluidization effectiveness of fluidized bed, and then analyzed the fluidized characteristic curve, it shows that density of fluidized bed is becoming even and stable with decrease of mean grain size, and further explains the existing of nonmagnetic grain contributes to fluidized effectiveness of fluidized bed. At last the result shows that fluidization effectiveness of magnetite powder D is the best.