Effct of the granule characteristics of MnZn ferrite on the magnetic properties has been studied.The granules were characterized by strength, deformation modulus, apparent density, and flow rate.The compressibility was evaluated by the porosity during pressing at constant rate of pressure elevation.It is shown that the intergranular pores in the green body resulted in the deterioration of core loss characteristics, and that the pressed density of green body could not be well explained only by the apparent density and the flow rate of granules.Plastic defromation of granules or friction of particles should be taken into consideration.