Abstract: The S content of the pyrites slag is up to 5.79% in a sulfuric acid plant in Chongqing.In order to produce iron ore concentrate,the S content needs to reduce under 1.5%.With controlling the grinding fineness as -0.074mm,accounted for 86%,the experiment uses CuSO₄ and H₂SO₄ as the activator,Sodium n-butylxanthate as the collector,2# gas as the foaming agent.Through the one coarse to two precise of the reverse flotation,it makes the Sulfur grade reduce to 1.32%.After dressing the flotation concentrate by magnetic separation,the grade of sulfur concentrate gets to 0.81%,the grade of the iron ore concentrate gets to 60.25%.The recovery of the Fe has got a good indicator of 82.45%.