The invention discloses a washing method of a magnetic medium of a magnetic separator. The washing method comprises the steps of 1, ultrasonically washing the magnetic medium; 2, soaking the magnetic medium with a descaling agent solution; and 3, flushing the magnetic medium with flushing water. The washing method of the magnetic medium of the magnetic separator has the advantages that the ultrasonic processing, soaking with the descaling agent and flushing with the flushing water are performed for washing the magnetic medium without discharging the whole structure; and moreover, nearly no damage is lead to the magnetic medium, so that the time can be saved, the service life of the magnetic medium is prolonged, and the cost is also saved.