The flotation separation of quartz from feldspar was performed by a single mineral flotation experiment, using N- dodecyl 1, 3- propanediamine(DN12) and sodium dodecyl sulfate(SDS) as the mixed collector.The effect of DN12 and SDS on the recovery rate of quartz and feldspar, as well as the flotation separation mechanism, were studied. The results show that the recovery rate difference between feldspar and quartz reaches the maximum one of 62.25%, under the flotation conditions of p H=2.0, DN12 concentration of 4.739×10-4mol/L, and SDS concentration of 2.38 ×10-4mol/L. The mixed collector is adsorbed on the surface of feldspar by physical adsorption, and on the surface of quartz by both physical and chemical adsorption, showing a higher capability of collecting quartz.