Porous carboxylic cation-exchanger has been synthesized by one-stage synthesis – suspension polymerization of methacrylic and acrylic acids (molar ratio 3:1) and triethyleneglycol dimethacrylate (15%) in the presence of a diluent. Ionization parameters (at different ionic strength) were defined from potentiometric curves as pKα – lg[(1- α)/ α] (α –ionization degree) dependence using Henderson-Hasselbach equation. The morphology of sorbent beads has been observed using SEM. Bovine serum albumin (IP 4.8) and lysozyme (IP 11.2) were model proteins for investigation of ionic strength influence at different pH on protein binding. Sorption regularities might be partially explained by carboxylic groups ionization increase with the increase of ionic strength, while the change affected sorption differently at different pH values.