Abstract: Direct and reverse flotation flowsheets are operated in two iron mineral processing plants separately.Tailing of the plants and the ash and the ash water of power stations are sent to the same tailing pond. Tailing water recycles to the plants to be reused. The tailing back-water contains calcium,magnesium, sulphate, fluorine ions and arsenic. The effects of these materials on the iron direct flotation are studied. The results show that the effects of calcium ion and sulphate ion on it are greater;magnesium ion and arsenic lower; fluorine ion non-effective. The dosage of flotation reagents can be controlled strickly during the production process, so that the bad effect of tailing back-water will bedecreased.