The invention relates to a beneficiation method for preparing iron concentrates through copper smelting slag floating copper tailing slag. The method comprises the steps that the floating copper tailing slag is subjected to magnetic separation pretreatment under the condition that the magnetic field intensity ranges from 1,000 Oe to 1,500 Oe, and magnetic tailing slag obtained; the magnetic tailing slag is ground through a vertical stirring mill till the content of the magnetic tailing slag with the meshes of -45 microns is 95%, and the ore grinding concentration of the magnetic tailing slag ranges from 50% to 65%; after the tailing slag is subjected to ore grinding through the vertical stirring mill, then first-section magnetic separation (roughing) is conducted under the condition that the magnetic field intensity ranges from 1,000 Oe to 1,500 Oe, iron concentrates 1 and tailings 1 are obtained through roughing; second-section magnetic separation (fine selecting) is conducted on the iron concentrates 1 obtained through first-section roughing under the condition that the magnetic field intensity ranges from 600 Oe to 1,000 Oe, and iron concentrates 2 and tailings 2 are obtained through magnetic separation; and the tailings 1 and the tailings 2 are subjected to scavenging under the condition that the magnetic field intensity ranges from 3,000 Oe to 4,500 Oe, magnetic products obtained through scavenging are iron middlings, and the iron middlings return to the third step to be subjected to first-section roughing. According to the method, the beneficiation technology process is short, cost is low, substances polluting to the environment cannot be generated in the iron concentrate recycling process, and industrial application can be achieved.