Abstract: The role of soluble starch in the flotation separation of feldspar from quartz was revealed through the single mineral flotation test, potentiodynamic test and absorption measurement. The results showed that soluble starch inhibited the flotation of feldspar and quartz when dodecylamine (DDA) and sodium dodecyl sulfonate (SDS) were used as mixed collectors. Compared to feldspar, the inhibition effect of soluble starch on quartz was stronger. The results of potentiodynamic test showed that the zeta potential of feldspar in soluble starch solution slightly shifted to the positive direction compared to that in pure water. However, the zeta potential of quartz in the soluble starch solution significantly shifted to the positive direction compared to that in pure water in the pH range of 5 to 7. The results of absorption measurement showed that when the dosage of starch was in the range of 20-80 mg/L, the adsorption capacity of quartz on the starch was larger than that of feldspar under the neutral pulp conditions. These results demonstrated that starch could hinder the adsorption of the collector on the quartz, and thus effectively depress the flotation of quartz. By contrast, the inhibition of starch on feldspar was weaker.