Circulating water is fed tangentially from the bottom to form a uniform rising water spiral in the separation area. The ore is fed into the middle of the column by the top feeder and dispersed into the separation area. In the separation area, multiple magnetic fields are superimposed, and the gangue minerals and conjuncture are affected by the spiral rising water impact force greater than the magnetic force + gravity, and overflow from the overflow tank with the water flow to form tailings. After monomer dissociation, the magnetic iron minerals are affected by the continuous downward magnetic force + gravity greater than the spiral rising water impact force in the composite magnetic field, and then discharged from the concentrate pipe at the bottom of the auto magnetic elutriation column to form concentrate.