The invention relates to a polystyrene sulfonic acid sodium cation exchange resin which is copolymerization prepared by the styrene-two ethylene benzene, through the compound which contains calcium ion transform, it purifies to the polystyrene sulfonic acid calcium resin, the compound which contains calcium ion is composed of calcium ion and its balance ion, the complexing agent, the acid alkalinity regulator and water. The balance ion is the chlorine ion; the complexing agent is: one kinds, two kinds or more than two kinds of the ethylene diamine four ethanoic acid, the second two support three amine five ethanoic acid, the ammonia three acetic acid, the citric acid and the calcium salt or sodium salt; the acid alkalinity regulator is hydrochloric acid and sodium hydroxide or hydrogen calcium oxide and so on abio-acid and alkali. The invention technical index has achieved to the standard of outward appearance,the calcium content, the potassium exchange quantity and the impurity (ammonium, heavy metal, arsenic, styrene and sodium) in the Japanese pharmacopoeia (JP14 e), the residual 1,2- dichloroethane content conforms to the standard about the organic solvent in the Chinese pharmacopoeia (2005 editions).