Abstract: It is difficult to have good separation index for Donganshan iron ore because of the high carbonate content.In order to find a suitable combination regulator and dosage，starch and CaCl₂ and their combinations as regulator on floatability of hematite，magnetite，siderite，iron dolomite and quartz single minerals were investigated respectively.The results show that the addition of single starch or CaCl₂ can not separate iron minerals from quartz.When the pH value is higher than 11，there is large difference in floatability of quartz and iron minerals when starch is used in combination with CaCl₂.One roughing，one cleaning flotation process was conducted on Dongshan mixed magnetic concentrate (50.88% Fe) using starch and CaCl₂ combination as modifier，and RA715 as collector.Flotation concentrate with iron grade of 64.06% and recovery rate of 61.96% was obtained，compared with the on-site process，iron grade and recovery were increased by 1.33 and 6.01 percentage points respectively.

Key words: Combine regulators, CaCl₂, Starch, Iron carbonate bearing in iron ore, Reverse flotation