Polymer-grafted ion exchange adsorbents were of great interest for the development of high-performance protein chromatography in biopharmaceutical and related fields. In this work, protein retention was systematically investigated in ion exchange chromatography packed respectively with dextran-grafted cation exchange adsorbents containing sulphopropyl (SP) ligand. SP Sepha rose XL and Capto S, and non-grafted cation exchange adsorbent, SP Sepharose FF, using five proteins. With an increase of buffer pHs, retention factors of proteins decreased among all the adsorbents, demonstrating the dominant role of electrostatic interaction for protein binding on cation exchange adsorbents. The evidences further revealed that the scattered positive charges on the surface of protein molecules, rather than net charge of protein molecule, determined protein retention on cation exchange adsorbent Likely, counterions induding NH4+,K+, Na+ and Mg2+ exhibited distinct influence on protein retention. It was well ascribed to solvent-mediated indirect ion-macromolecule interactions and direct ionmacromolecule interactions. Compared with SP Sepharose FF, polymer structure in dextran-grafted cation exchange adsorbents ultimately brought about different ligand distributions and smaller pore sizes, thereby regulating protein retention in cation exchange chromatography. By comparing the retention of myoglobin and beta-lactoglobulinB in SP Sepharose XL and Capto S, we reasonably speculated that the enhancement of nonelectrostatic interaction caused by reducing the space arm length was a major reason for an increasing retention factor of myoglobin in Capto S. The results in this research help us understand adsorption mechanism of protein in polymer-grafted adsorbents and give scientific guidance for the development of chromatographic materials. (C) 2020 The Chemical Industry and Engineering Society of China. and Chemical Industry Press Co, Ltd. All rights reserved.