Abstract: Ultrafine barium ferrite magnetic powders were synthesized successfully by sol-gel （method.）The hydroxide precursor particles are formed in gel solution contaning ethanol and water at a ratio of 1:1.7 and Ba²⁺and Fe³⁺cation at a ratio of 1.15:12 and NaOH as coprecipitation ageant.The hydroxide precursor was pre-heated at 300℃ for 1h,and then calcined at 800℃ for 5h.The XRD tests reveal that ultrafine barium ferrite particles are formed and the particles size is 42.0nm closing to the theoretical single-domain size of 40nm.