When the raw materials flow into the tank body of the wet drum magnetic separator, firstly, the flowing direction of the raw materials is the same as the rotary direction of the magnetic drum, the iron magnetite materials are attracted to the surface of drum. This is the first separation. In the second step, the flushing water below flush the raw materials back for the second separation. This time the flowing direction of the raw materials is opposite to the rotary direction of the magnetic drum. Then along with the rotation of drum, the iron magnetite materials on the surface of drum will finally leave the magnetic field and fall to the ore concentrate box under gravity. Also, the flushing water above helps to flush the iron magnetite into the ore concentrate box. The weak magnetic and non-magnetic materials cannot be attracted and will flow to the discharge pipe for tailings.