An analytical equation is derived for the kinetic reaction of Barium Ferrite, considering the particle size distributions of raw materials. The powder of Barium Carbonate have the logarithmic normal distributions. The total degrees of reaction are calculated for the reactions at the temperature T=960, 1,040, 1,120, 1,200, and 1,260 ℃ with various time and compared with those values, determined by means of vibrating sample magnetometer. Jander equation can be applied to the Barium Ferrite reaction, if the particle diameters of Barium Carbonate are equal. And the activation energy of the reaction ( E₂=55.8 Kcal per mole ) is obtained according to Arrhenius equation.