Abstract: SLon high intensity and medium intensity magnetic separators are mainly used to tailings discarding in the oxidized ore processing flow of Si Jiaying iron mine. The separation efficiency of magnetic separators influence the recovery of final concentrate and following separation flow directly. In this paper, magnetizing current intensity was changed to investigate the separation efficiency and magnetic field intensity. The tests results indicated that the recommended current intensity range of high intensity and medium intensity magnetic separators was 400～600A and 600～800A, respectively. At this time, the grade and recovery of concentrate was close to highest value. The mechanism of concentrate indexes which along with the changes of magnetizing current intensity was analyzed. The recovery of fine magnetic mineral particles increased with the increase of magnetizing current intensity, meanwhile, the grade of concentrate increased to the highest value when the magnetizing current intensity was closed to the recommended range. The optimization of recommended current intensity range was significant to the steady production and energy-saving and cost-reducing of Sijiaying iron mine.