The invention discloses a method for performing flotation separation on garnet from magnetic separation brown iron ore concentrate. The content of iron in raw mineral materials is 47.51-49.32%, and the content of the garnet in raw mineral materials is16.24-14.91%. The phase analysis shows that the iron mainly exists in the form of the brown iron ore and seldom in the form of haematite and hemimorphite, and gangue mineral mainly exists in the form of the garnet and silicate and seldom in the form of silica mineral. According to the method, sodium carbonate serves as a pH regulator, basic fuchsin and hydroxymethyl cellulose serve as inhibitors of the garnet, calcium oxide serves as an activator of the brown iron ore, and oxygen fossils preserved soap serves as a collector of the brown iron ore. By means of the method, the flotation separation on the brown iron ore and the garnet can be achieved, and grade of the grown iron ore concentrate is effectively improved. Under the condition of the feeding iron content of 47.51-49.32%, after the flotation separation, iron ore concentrate with the iron content of 55.18-56.70% and the recovery rate of 85.11-87.63% is obtained.