The　study　focused　on　the　synthesis　and　applications　of　an　aminophosphonic　acid　chelating　fiber　(PAN-PNa)　for　the　deep　removal　of　Ca2+　and　Mg2+　from　aqueous　solutions　in　the　chlor-alkali　indus-try.　As　an　effective　material　for　the　replacement　of　aminophosphonic　acid　resins,　PAN-PNa　achieved　outstanding　adsorption　results　for　Ca2+　and　Mg2+.　The　material　was　prepared　by　the　Kabachnik-Fields　one-pot　reaction　using　an　amine-based　fiber　(PAN-PEI)　as　precursor.　The　saturated　adsorp-tion　capacities　of　PAN-PNa　for　Ca2+　and　Mg2+　were　significantly　higher　than　those　of　existing　aminophosphonic　acid　resin,　reaching　3.07　and　3.12　mmol/g,　respectively.　These　values　were　sus-tained　even　at　low　ion　concentrations,　and　in　a　wide　pH　range　of　3-11　and　3-10,　respectively.　The　adsorption　of　the　ions　reached　equilibrium　within　5　min,　which　is　an　excellent　improvement　from　conventional　granular　adsorbents　(about　40-80　min).　The　excellent　performance　of　PAN-PNa　was　attributed　to　its　phosphoramidate　group　and　special　nano-towed　structure.　Therefore,　by　exhibit-ing　both　fast　adsorption　rate　and　high　adsorption　capacity　at　low　ion　concentration,　PAN-PNa　is　a　promising　new　material　for　the　deep　removal　of　Ca2+　and　Mg2+　from　aqueous　solutions.