Abstract: In order to solve the problem of over-stable foam in the hematite concentrate of direct flotation, foam stability was investigated from the aspects of sodium oleate concentration, solution temperature, pH value, and the grain size and concentration of fine hematite concentrate. The results showed that the concentration of sodium oleate had a significant impact on foam stability. With the increase of sodium oleate concentration, foam stability increased firstly, then decreased, and finally remained basically unchanged. The most stable foam appeared when the concentration was 1×10^-3 mol/L. Under the condition of low concentration of sodium oleate, the temperature had a certain effect on foam stability. At high concentration, temperature had no significant effect on foam stability. In the condition of low sodium oleate concentration, the foam stability was the strongest with the pH value of 6~8. In the condition of high sodium oleate concentration, the foam stability was the strongest with the pH value of 4~6. The stability of three-phase foam was related to the grain size and the concentration of fine hematite concentrate. Under the condition of fine grain size and high concentration, the stability of foam was strong.