Abstract: The sponge iron making with iron sludge produced during DSD acid-making can be used for not only general metallurgy but also iron-carbon bed to treat DSD acid oxidation wastewater. It is pointed out that under the condition of the temperature of 1120℃, the reaction time of 16 min and the carbon content of 27%, the metal transformation rate of sponge iron used for general metallurgy is up to 90%. But the optimal carbon content is 29% for iron sponge to treat DSD acid oxidation wastewater. Under condition of the wastewater's pH value of 3 to 5 and the reaction time of 40 min, the removal rates of COD_Cr and color are 68% and 90%, respectively. The BOD/COD ratio is up to 0.425 when DSD oxidation acid water is treated with sponge iron. As Fe₃C and other materials contained in sponge iron formed so innumerable micro-batteries between iron and other elements to oxidate and deoxidize the organics in wastewater, the pollutants became degradable and the biodegradation of wastewater was promoted. The micro-sponge-shape of sponge iron is so developed that its special surface area is greater and its activity is higher, so it is the best alternative of general iron powder.