The operat ing technology of t reating sew age and sludge by g as washing at the 2500m³ blast furnace in Maanshan I ron and Steel Works and the improvement af ter putting it into production are int roduced in this paper, including the technological routines before and after the improvement, once -through precipitation, concentration at tw ice, cooling, sludge t reatment and water stability, etc.The emphasis is putting on the product ion running effect and economic benef it af ter the improvement.