Abstract: A sulfur-oxidizing bacterial strain was isolated from sewage sludge using liquid selective medium and then purified on solid selective medium.The bacteriam can metabolize sofur or S₂O₃^2- to SO₄^2- during growth.The sulfur-oxidizing strain is Gram-negative,and has ability to swim.After three days of cultivation,the results showed that the pH of medium decreased.After one week,the pH of the medium dropped to about 0.6,which suggests sulfur oxidizion is taken place.The concentration of the sulfate was tested by using ion chromatography,and the results showed that the concentration of the sulfate increased from 249.2 mg·L^-1 to 3 679.7 mg·L^-1.The sulfur-oxidizing bacterium was then inoculated into the FeS medium,as expected,the FeS was oxidized and the media became lighter in color.