The necessity of applying materials with high degree of fineness in many industrial branches requires using modern technology in mechanical processing, which will assure demanded particle size distribution of product and should decrease of consumption energy. The industrial grinding devices, which work in the high-energetic fluidized bed conditions are the perspective resolution. Comminution of granular material relies on keeping up a turbulent fluidization in the grinding chamber of the fluidized bed opposed jet mill, which is a result of collisions source of air counter-fluxes. The state of pulsatory fluidization is created in the lower zone of the fluidized bed, where take place intensive mixing and comminution of grains by gas bubbles and grain agglomerates. The state of fountain fluidization is created in the upper zone of the fluidized bed, which is characterized by carryover of grains in the zone of high velocities in the centre core of grinding chamber, then by gravitational falling of coarse grains near walls and by carrying away of the small grains by the flowing gas into the separation system. Occurrence of collision source of air counter-flux and turbulent fluidization state in the grinding chamber makes it possible to obtain high-energetic fluidization layer. This layer in turn ensures an effective comminution of tested granular material. However basis of the comminution mechanism of grains in the fluidized bed opposed jet mills aren't satisfactory explained. It results from the difficulties to determine the influence of all parameters process on the evolution of particle size distribution of milling product. The theoretical analysis of the comminution mechanism of grains in the grinding chamber of the fluidized bed opposed jet mill are presented in the part 2 of article. The researches were performed on a laboratory mill, which is designed for fine grinding of granular materials. The experiment contained grinding of selected narrow size fractions of limestone for optimum operating conditions of the fluidized bed opposed jet mill. The analysis showed that comminution in the mill takes place in three zones as a result of superficial attrition of grains, dynamic breakage of grains and cleavage of grain agglomerates. lntensification of individual processes depends on many parameters, e.g.: fluidized air energy, mass of materiaIs creating the layer, the way of grain collisions, structure and resistance of grains (mono-crystals, poly-crystals, agglomerated).