The so-called resistance characteristics of fluidized bed  refers to relationship of the resistance pressure drop of fluidized gas through material layer and the cold fluidizing velocity calculated according to the bed cross-sectional area. For the materials layer with a certain thickness, if its resistance does not reach the initial fluidization velocity, it shall follow the rule of quadratic. After it reaches the initial fluidization velocity, the resistance almost has no relation with fluidization; it is basically equal to the gravity of the bed material.