The utilization of thermal-treated metallurgical sludge as cement admixtures has been studied in this paper.X-ray diffraction (XRD) showed that all of three kinds of thermal-treated metallurgical sludges (S-I-850,S-II-850, and S-III-850) contained lots of active minerals.Scanning electron microscopy (SEM) showed that a lot of sub-2μm particles and micro-pores have a large distribution on the surface of thermal-treated metallurgical sludges.The activity indexes of S-I-850 for 3d, 7d and 28d were 54.7, 68.9, 74.1, respectively.It reaches the requirements of activity indexes of class-B steel slag and fly ash.The leaching test results indicated that mortar CS-I-850 was effective at immobilizing heavy metal ions.S-II-850 and S-III-850 also could meet the requests of activity indexes of the class-B steel slag and fly ash, but these two kinds of metallurgical sludges maybe have less application value for cement admixtures since there were a large amount of organic matters before incineration.