This study analyzed the organics and content of metal ions in extracellular polymeric substances (EPSs), tightly (TB-EPSs) and loosely (LB-EPSs) bound EPSs of granular sludge with simultaneous removal of organic matters and ammonia nitrogen, studied the dynamic variation of metal ions in EPSs from granular sludge with different particle sizes and the change of zeta potential before and after cation exchange resin (CER) treatment. Results showed, with particle size increasing, the protein content gradually increased, the content of polysaccharide basically unchanged; the content of Ca, Mg, K, Na and Zn also increased, whereas others did not show a consistent regularity. The existence of metal ions reduced zeta potential of EPSs. The existence of metal ions helped to the adhesion among granules, in order to form a granule with bigger particle size. (C) 2014 Elsevier Ltd. All rights reserved.