We calculated the characteristics of phosphoric cation exchanger and studied up on an accurately computable method to ion exchange capacity for type of potentiometric titration curve. It can explain a linear equation to the experimental pK values versus χ in phosphoric cation exchanger. The ΔpK values were obtained from the slope of linear equation. Also the experimental pK values at χ=0.5 were accorded well with theoretical data. When it is titrated with NaOH and Ba(OH)₂ solutions, a good agreement between experimental and theoretical pK values for various χ was seen in all the potentiometric titration curve, The inflection point of potentiometric titration curve can know that in the case of divalent ions are larger changed than that for monovalent ions. And if the relation between g values and ∂pH/∂g was plotted to the Lorentz distribution curve, it can accurately evaluate the ion exchange capacity.