Chemical and mineral compositions, the surface morphology of steel slag were evaluated in this study. On this basis, treatment effect of acidic Zn2+-containing wastewater was investigated using the slag as a water treatment material, and then mechanism of removal Zn2+ was discussed. The results showed steel slag was a suitable material for treatment of acidic heavy mental wastewater. Under conditions of slag size fraction of -1.2+0.15mm, slag concentration of 30 g∙L-1, stirring speed of 150rpm for 30 min, removal rate of Zn2+ was 98.59%, Zn2+ concentration in wastewater was reduced from 100 mg/L to 1.41 mg/L, and pH value was increased from 2 to 6.4. Filtrate after treatment reached the first discharge standard in integrated wastewater discharge standard (GB8978-1996). Appearance of Zn (OH)2 diffraction peaks in XRD pattern showed that Zn (OH)2 had covered on steel slag surface, and Zn2+ removal included four main processes: production of OH- from hydration reaction of aSubscript textctive calcium silicate in steel slag, generation of Zn (OH)2 precipitation in wastewater, adsorption and settlement of Zn (OH)2 on surface of steel slag and removal of Zn (OH)2 from wastewater by filtration.