The invention relates to a magnetite beneficiation process capable of fully releasing mill capacity. The magnetite beneficiation process includes the steps that raw ore is subjected to three-section breaking and secondary dry separation and then ultrafine-ground through high-pressure roller milling, after high-pressure roller milling products are screened through screening equipment, undersize products are fed into a wet type preselection magnetic separator, wet type preselection rough concentrate is subjected to ore grinding, classifying, magnetic separating and reselecting, partially-qualified concentrate is obtained, reselecting process tailings are fed into second-section ore grinding after being subjected to concentration magnetic separation, second-section ore grinding products are subjected to magnetic separation, fine screening classification and elutriating selecting, and qualified concentrate is obtained. As the high-pressure roll milling products are subjected to wet type preselection, a large quantity of qualified tailings can be thrown out, the mill entering quantity is reduced, and the ore milling cost and the energy consumption are reduced; the partially-qualified concentrate can be recycled in advance through the magnetic and gravity combined separation process by means of the density difference between iron minerals and lean coenobium; and in the whole process,the mill capacity can be fully released, energy saving and consumption reduction are achieved, compared with current conventional processes, the effective volume of a ball mill can be reduced to be 50% or below, the investment can be greatly reduced, and the production cost is reduced.