Abstract: In order to improve the flotation indexes of Qidashan iron ore， flotation collector DJW-II which is a new self-made reagent containing both N-H and O-H groups was made to use for research of flotation separation of mixed magnetic separation concentrate， JW series surfactants are used as auxiliary collectors. The results show that under the conditions of the flotation temperature 21 ℃， and pH 9.0， the dosage of collector DJW-II 125 g/t in roughing and 50 g/t in concentration， surfactant JW-4 0.6 g/t， inhibitor carboxymethyl starch sodium 250 g/t， the flotation process of one roughing and one concentration is adopted to obtain flotation concentrate of 50.98% yield， 68.08% grade and 69.85% recovery. The results showed that the flotation concentrate was improved by improving the foam volume， half-life period and foam viscosity， in turn the flotation index was improved. Finally， the structure of compound collectors， water molecules and relative ions Ca2+， Cl-， through Materials Studio software builds a molecular model for the bubble membrane structure， and Forcite module was used to do geometry optimization and dynamics. After adding auxiliary collector， collector molecular reactive group adsorption closer with the middle of the water molecules， and bubble performance test after adding auxiliary collector bubble viscosity change was consistent.

Key words: Iron ore, Reverse flotation, Auxiliary collectors, Half-life period, Viscosity