Porous cation-exchange resins have been synthesized by water-dispersion polymerization of acrylic and methacrylic acids at the ratios 1:3, 1:4, and 1:5 and cross-linking agent triethylene glycol dimethacrylate. The ionization of these resins is characterized by decreased dependence of effective ionization constant from ionization degree α after the achieving of α =0.5. The morphology of resin has been shown by SEM method. BSA sorption study indicates sorption capacity growth with the increase of amount of acrylic acid units in the resins and the complicate character of sorbent structure influence on BSA sorption capacity. The influence of resin ionization, swelling and chain flexibility on sorption been discoursed.