Abstract: Bio-hydrometallurgical technology is very efficient for handling poor，complex and fine ores and has advantages that conventional mineral processing and metallurgical methods can't have.Extracellular polymeric substances（EPS）plays a very important role in the extraction of metal ions from sulfide ores in the bio-hydrometallurgical process.Analysis is made of the EPS extracted by sulfuric acid method and the method of formaldehyde plus sodium hydroxide and the function of EPS and metal ions by UV spectrophotometer.The results show that there is only complexation between EPS and Fe³⁺ ions，thus verifying that it is through the oxidation function of the Fe³⁺ions in the complex between EPS and Fe³⁺ ions that EPS enables the metal sulfides to degrade.

Key words: Bio-hydrometallurgy, EPS, Sulfuric acid method, Method of formaldehyde plus sodium hydroxide, UV Spectrophotometry