The removal characteristic of phosphorus(P)from wastewater by alum sludge from waterworks was studied in adsorption test.The results showed that the phosphorus adsorption of alum sludge(AS)fitted the Langmuir adsorption isotherm equation,and phosphorus adsorption capacity was up to 12 500 mg/kg,while it went down with the increase of pH value and went up with the increasing mass ratio of AS and phosphorus.Compared with single use of coagulant,the simultaneous usage of polymeric aluminum chloride(PAC)and AS could improve the removal rate of phosphorus and reduce the amount of PAC,so AS could strengthen the removal effect of phosphorus.