This paper presents an original approach to study the dependence of the sulfonation conditions of polycarbonate membranes on the separation performance and their influence on the membrane morphology. The degrees of sulfonation of polycarbonate membranes can be prepared by various dosages of sulfonic acid in the sulfonation process. The degree of sulfonation and polymer concentration in casting solution showed the significant effect on the membrane formation in wet phase inverse process. It was found that the permselectivity of sulfonate asymmetric polycarbonate membranes showed a strongly enhancement by increasing the degree of sulfonation. Both of the permeation rate and permselectivity increased with increasing the degree of sulfonation of polycarbonate membranes. It was found that the separation performances of the sulfonation membranes were dominated by the enhancement of hydrophilic property of modified membranes.