Antimony (Sb) pollution in Sb mining areas has been of growing environmental concern. However, limited information is available on environmental behavior and biogeochemical process of Sb. In the present study, complexation of Sb(III) with extracellular polymeric substances (EPS) from cyanobacterium Synechocystis sp. was investigated using excitation-emission matrix (EEM) fluorescence spectroscopy. Two protein-like fluorescence peaks were identified in the EEM spectra of EPS. Fluorescence of both peaks was clearly quenched by Sb(III). The quenching constants (logK_a) and the binding constants (logK_b) for peaks A and B were in the range of 3.21-4.13 and 3.22-4.14, respectively. The interaction between EPS and Sb(III) is spontaneous and endothermic. The binding of Sb(III) to EPS is dominated by the hydrogen bonding and Van der waals forces. FTIR analysis showed that polysaccharides in EPS also participated in complexation EPS with Sb(III).