Bsi20310 exopolysaccharide (Bsi20310 EPS) was secreted by a bacteria named Pseudoalteromonas sp. Bsi20310, isolated from Antarctic Sea ice. Crude Bsi20310 EPS was prepared by precipitation of the culture solution with ethanol, with proteins removed by using chloroform and butanol preparatorily. The results showed that Bsi20310 EPS improved the FeCl3 coagulation performance on synthetic water-soluble dye reactive red X-3B dyeing wastewater, obviously. The optimum coagulation enhancement of Bsi20310 EPS expressed by decolorization rate is from 16% to 84%, at pH near 10, Fe(Ⅲ) concentration of 0.98 mmol·L-1 and Bsi20310 EPS concentration of 150 mg·L-1, respectively. Fourier transform infrared spectroscopy (FTIR) was used to investigate the functional groups of Bsi20310 EPS, Fe(Ⅲ)-Bsi20310 EPS floc and Fe(Ⅲ)-Bsi20310 EPS-reactive red X-3B floc. The spectra showed that Bsi20310 EPS contained a large number of functional groups such as —OH, —COOH and glycosidic bond. Some certain functional groups of Bsi20310 EPS changed being combined with Fe(Ⅲ) hydrolysate. For instance, narrow peaks at 3 429 and 1 650 cm-1 became wide; the peak at 2 921 cm-1 weakened or disappeared; the peak at 1 242 cm-1 red-shifted slightly; peaks in the region of 1 151-1 038 cm-1 became single and sharp, etc. The change in spectra indicated that —OH, —OOH and glycosidic bond might be the main functional groups. The study suggested a bright prospect of Bsi20310 EPS performing as an approach to safe and effective microbial coagulation enhancement.