Abstract: The influencing factors(e.g.pH, competing anions and citric acid) of phosphorus adsorption capacity of 800℃-heated calcium-rich attapulgite were studied.The results showed that pH had no influence on phosphorus adsorption capacity in acidic conditions, while in alkaline conditions, pH had a certain effect on the phosphorus adsorption when it was in the range of 8-10.The effect of pH on phosphorus adsorption capacity was mainly via changing the amount of exchangeable metals(Mg and Ca) and the Zeta potential.It was noted that HCO₃^- inhibited phosphorus adsorption of NCAP800 mostly when the concentration of HCO₃^- was 5-20 mg/L, followed by SO₄^2-, NO₃^- and Cl^-, which had no effect on phosphorus adsorption.The inhibiting effect was mainly through competing adsorption sites, which reduced phosphorus adsorption capacity of NCAP800.The low citric acid concentration(0-5 mmol/L) had a slightly lower effect on phosphorus adsorption than that of high citric acid concentrations(5-50 mmol/L), resulting from the inhibition mechanism of competing adsorption sites on the NCAP800 surface.