The invention relates to a device and a method for reducing hematite-containing materials by utilizing microwave heat treatment and carrying out magnetic separation. The device comprises a material bin, a screw feeder, a star type feeding machine, a preheating reacting furnace and a microwave magnetic separator. When the magnetic separation is carried out, the materials are crushed and then added to the material bin, powdery materials enter the preheating reacting furnace through the screw feeder and the star type feeding machine for preheating, and the preheated powdery materials enter the microwave magnetic separator through an air inlet pipe for the microwave heat treatment and the magnetic separation; products subjected to the magnetic separation are discharged through an ore discharge pipe from a discharge port, and other materials are discharged through an outlet pipe from the discharge port. The device disclosed by the invention can be used for reducing the weak magnetic Fe2O3 contained in the materials into strong magnetic Fe3O4 through the microwave heating and separating the iron ore concentrates through the magnetic separation, integrally and simultaneously carries out the reduction and the magnetic separation, has the advantages of small investment, low energy consumption, large treatment quantity, water saving, no air pollution, wide application range and relatively popularization prospect, is simple in equipment, and can be used for treating multiple hematite-containing materials which include ores, such as steel slag, low-grade limonite and iron ores.