Reverse　flotation　technology　is　one　of　the　most　efficient　ways　to　improve　the　quality　and　reduce　impurity　of　iron　concentrate.　Mineral　processors　dealing　with　hematite　face　a　challenge　that　the　flotation　results　of　reverse　flotation　of　hematite　are　poor　in　presence　of　siderite　using　fatty　acid　as　collector,　starch　as　depressant　of　iron　minerals　and　calcium　ion　as　activator　of　quartz　at　strong　alkaline　pH.　In　this　work,　the　effect　of　siderite　on　reverse　anionic　flotation　of　quartz　from　hematite　was　investigated.　The　effect　mechanism　of　siderite　on　reverse　flotation　of　hematite　was　studied　by　solution　chemistry,　ultraviolet　spectrophotometry　(UV)　and　Fourier　transform　infrared　spectroscopy　(FTIR).　It　was　observed　that　siderite　had　strong　depressive　effect　on　quartz　in　flotation　using　sodium　oleate　as　collector,　corn　starch　as　depressant　of　iron　minerals　and　calcium　chloride　as　activator　of　quartz　at　strong　alkaline　pH.　The　starch　was　adsorbed　onto　calcium　carbonate　by　chemical　reaction　which　was　formed　by　CO3　(2-)　from　siderite　dissolution　and　Ca2+　from　calcium　chloride　as　activator　of　quartz　and　precipitated　on　the　surface　of　quartz,　which　resulted　in　improving　the　hydrophilic　ability　of　quartz.