To mix the converter roller steel slag powder with heavy metals contaminated soil, the remediation effect of steel slag powder on heavy metals contaminated soil were tested by X ray diffraction(XRD) and Fourier transform infrared spectroscopy(FTIR) to elucidate the mechanism of remediation. The results show that the steel slag powder has a good repairing effect on Cd2+, Cu2+, Pb2+, Ni2+ and Zn2+ in the polluted soil and the best repairing time is 37d. In the early stage(13d), the mixture of steel slag powder and heavy metals contaminated soil has a relatively high alkaline environment, and the formation of Cu(OH)2·2H2O, Ni(OH)2·2H2O and Zn(OH)2 is accelerated through ion exchange. At the middle stage(314d), with the accelerated hydration of Ca2SiO4 to form a gel(C S H), SiO4-4 begins to react with Ni2+ and Zn2+, at that time ion exchange and gel solidification play a role. In the later stage(1428d), Ca2SiO4 continue to hydrate to form a large amount of C S H, and SiO4-4 reacts with Ni2+ and Zn2+ to become the dominant reaction. In the later stage, the concentration of OH- in the mixture of steel slag powder and heavy metals contaminated soil decreases in the gel solidification, and the more hydrated Ca2SiO4 solidified with Cd2+, Ni2+ and Zn2+ to form Cd2SiO4, Ni2SiO4 and Zn2SiO4.