The mixture of five yeast strains obtained from soil could remove about 85% TOC of oil-rich wastewater in batch test.While the highest MLSS was obtained at an N:C of 1:5, the oil removal decreased with the increase of N:C during yeast sludge cultivation. Ammonium chloride was the best nitrogen source for yeast cultivation from the viewpoint of yeast growth and oil utilization. An ammonia concentration of over 1300 mg l-1 led to mass death of yeast at a pH of 5. The ammonia concentration should be controlled at a level of 1000 mg l-1 or lower.