Abstract: In order to investigate the bio-activities of the extracellular polysaccharide（EPS）from the marine bacteria in the Guangxi Beibu Gulf，the marine bacteria of EPS-producing were isolated from water/mud samples by LB-aniline blue medium. Phenol-sulfuric acid method was used for measuring the yield of the EPS. The marine bacterial strains with high-yield of ESP were further identified by the sequence analysis of 16S rDNA. The molecular weight and the preliminary structure of the EPS were tested by Gel permeation chromatography（GPC）and infrared spectrometry，respectively. Finally，the cytotoxicity of the EPS on Vero cells and the inhibitory effect of the EPS on Hela cells were tested by the MTT method. The results showed that totally 167 marine bacteria producing EPS were isolated from sea water/mud of mangrove，one of which（named BHc-09）yielded ESP as high as 0.306 mg/mL and was identified to be Vibrio by the analysis of its 16S rDNA sequence. The molecular weight of the EPS from BHc-09 was 184.5 kD，and there was uronic acid in the EPS structure. The EPS produced by BHc-09 presented no cytotoxicity on Vero cell，but significantly inhibitory effects on tumor cells. The results suggested that an EPS-producing marine Vibrio was successfully isolated and identified，and its extracellular polysaccharide has anti-tumor activity.

Key words: marine Vibrio, extracellular polysaccharide, isolation and identification, anti-tumor