A model is presented to evaluate the concentration of species in a citric solution for preparing barium ferrite powder. The evaluated concentration of species provides valuable information and help in selecting the optimal condition for preparation of the barium ferrite powder using the citrate process. The influence of the molar ratio of cations and citric acid on the formation of barium ferrite is studied. The formation temperature of barium ferrite decreases as the ratio increases. When the molar ratio of cations and citric acid is 13:20, the barium ferrite can completely form at 700 degrees C.