A vacuum extraction (VE) treatment was utilized as a new method to prepare the sol-gel precursor for the barium ferrite thin film. The phase formation of barium ferrite can be enhanced when precursor was treated by vacuum extraction. Thin films with Fe/Ba ratio of 2.28 easily form single barium ferrite phase and possess better magnetic properties. In contrast, films with Fe/Ba = 11.4 are difficult to form single phase barium ferrite. The effect of Fe/Ba mole ratio is also discussed in this paper.