A magnetite pretreatment device comprises a cutting system, a screening system, a washing system, a magnetic separation system and a flotation system which are sequentially arranged from top to bottom. According to the cutting system, the ore raw materials are cut three times in sequence, the cutting effect is good, the efficiency is high, and the situation that during the follow-up machining process, the ore size is too large, so that a machine gets stuck, can be effectively prevented. Meanwhile, the cutting system can adjust the number of the parts, extending into the corresponding working grooves, of the rotary cutters according to the size of ore raw materials and the cutting requirements, so that the cutting efficiency is changed, and the work scheduling is flexible. According to thescreening system, the mineral aggregate is screened through the vibration and the wind power, so that the screening efficiency is effectively improved. According to the magnetic separation system, through the design of the two layers of conveying crawler belts and the shifting plates, more magnetic separation heads can be used for magnetic separation at the same time, the magnetic separation efficiency is improved, and themetallic magnetite can be rapidly and effectively separated out.