To investigate the relation of crushing effect of magnetite and energy under mechanical impact, the drop weight impact experiments, electron microscope observation test, and atomic absorption spectrometric analysis tests were carried out. The fragmentation characteristics and the separate mechanism of mineral particles of banded magnetite-quartzite under impact were analyzed, and the theoretical relations between energy density and size fractal dimension of fragments, average fragment size, and mineral particle separation efficiency were obtained. The study found that there were fractal characteristics in size distribution fragments, and the breakage extent of magnetite-quartzite under impact could be described more comprehensively with size fractal dimension and average fragment size. The fragment size under the separation of mineral particles was consistent with size of minerals, and the smaller the fragment size, the more remarkable the mineral separation is. The morphology and optical characteristics of separated particles after the impact crushing were closer to the mineralogical characteristics of the ore in comparison with the products of the second stage grinding, and the total iron grade of separated magnetite particles produced from impact crushing met the requirement of beneficiation for it was higher than that produced from the second stage grinding. The results showed that the average particle size decreased by cubic polynomial with the increase in energy density. The fractal dimension increased exponentially, and the separation efficiency of mineral particles increased by cubic polynomial. The specific energy consumed in magnetite ore processing could be reduced by increasing the breakage extent of magnetite-quartzite, the mass ratio of mineral particles, and energy density during crushing, and directly conducting magnetic separation after sieving mineral particles.