Abstract: Flotation behavior of ultrafine hematite and the effect of five types of depressors（sodium hexametaphosphate, sodium silicate, sodium pyro-phosphate, starch, sodium humate）on ultrafine hematite recovery in NaOl flotation system were researched. The results show that ultrafine hematite reaches to good floatability when the concentration of sodium oleate is 4×10-4 mol/L and pH value is 10. The five types of depressors all have obvious depression on ultrafine hematite flotation, organic depressors have a better depression effect than inorganic depressors, and the depression effects of the five depressors are in the order of starch＞sodium humate＞sodium pyro-phosphate＞sodium hexametaphosphate＞sodium silicate.

Key words: Ultrafine hematite, Flotation, Sodium oleate, pH, Depressor