Abstract: Modification is an effective method to improve the cementitious activity of electrolytic manganese residue (EMR). The electrolytic manganese slag was modified by adding modifier (lime) or roasting method. The effects of different electrolytic manganese slag content and different roasting temperature on the mechanical properties of concrete were studied. The results showed that the compressive strength of the concrete prepared by the modified electrolytic manganese slag with the blending amount of 3%～10% and the electrolytic manganese slag calcined at 300～500 ℃were 40.1～43.5 MPa and 36.6～42.7 MPa respectively at the age of 28 d. When the content of modified electrolytic manganese slag was 10%, the compressive strength of concrete with electrolytic manganese slag modified by mixed quicklime and roasted at 450 ℃were 2 MPa and 5 MPa respectively, higher than that of concrete without electrolytic manganese slag. Under the condition of lime modification or calcination at 450 ℃ for 1 h, CaSO₄·0.5H₂O in electrolytic manganese slag was completely converted into CaSO₄·2H₂O and anhydrite, more C-S-H gel and AFt were generated in the prepared concrete and the mechanical properties of concrete were enhanced. It showed that CaSO₄·2H₂O and anhydrite could promote hydration and improve the early compressive strength and flexural strength of concrete.