The blast furnace water quenched slag has characteristics such as porous and superficial roughness, so it can be modified and cranked out a filter media. The treatment efficiency of domestic sewage with water quenched slag biological aerated filter (BAF) was researched in this paper. And the removal rate of organic compound, ammonium, SS, and chroma was also investigated. The results showed that the quality indexes of the domestic sewage after treatment met the primary standard of the national integrated wastewater discharge standard (GB8978-1996). So the purpose of the waste harnessed by other waste is achieved. The applicative prospect of blast furnace water quenched slag on domestic sewage treatment is very broad.