Abstract: The leaching solution of Zijinshan Copper Mine is adopted as the mother liquor to extract the Acidithiobacillus ferrooxidans to identify the purification and physiological features of bacterial strains.Then the nature of the extracted EPS and its fractions are analyzed and surveyed.Under 6 group combining conditions with addition of Fe3+ and the strain or not，deactivation of the strains or not，EPS separating from living cells or not，the law of potential variation of oxidization and reduction in leaching process of Zijinshan copper samples are investigated.Then the reasons for reforming this law are revealed one by one.The studies show that the leaching of EPS to the metallic sulfide ore can not do without its secreted living cells. 

Key words: Acidithiobacillus ferrooxidans, EPS, Properties, Leaching function