Flotation　is　the　most　known　beneficiation　method　for　the　separation　of　complex　and　refractory　iron　ores.　As　a　typical　iron-containing　silicates,　it　is　difficult　to　separate　chlorite　from　specularite,　because　of　the　similar　surface　physicochemical　properties.　In　this　study,　the　selective　depression　effect　of　sodium　hexametaphosphate　(SHMP)　was　conducted　via　the　cationic　micro-flotation.　The　surface　adsorption　mechanism　between　SHMP　and　the　two　mineral　surface　was　explored　through　surface　adsorption　amount　tests,　Zeta-potential　measurements,　Fourier　transform　infrared　(FT-IR)　and　X-ray　photoelectron　spectroscopy　(XPS)　analyses.　The　micro-flotation　results　indicated　that　SHMP　could　selectively　depress　around　90%　of　chlorite,　while　its　effect　on　the　floatability　of　specularite　was　negligible　(＜20%　depressing).　The　surface　adsorption　amount　tests,　Zeta-potential　measurements　analysis　demonstrated　that　SHMP　selectively　adsorb　on　chlorite　surface　while　on　the　surface　of　specularite　is　feeble.　The　further　surface　adsorption　analysis　via　FT-IR　and　XPS　proved　that　SHMP　selective　adsorption　occurred　on　the　chlorite　surface　mainly　by　chemisorption　mainly　through　the　chelation　reaction　between　O　in　the　phosphate　groups　of　SHMP　molecular　and　metal　ions　on　surface　of　chlorite.