With Na2SiO3, NaOH and Ca(OH)2 preparation of alkali solution, then steel slag was activated using alkali solution. The effects of Na2SiO3 amount, NaOH amount and Ca(OH)2 amount on the mechanical property of the alkali steel slag cementations materials were studied in order to obtain optimal mechanical properties of alkali steel slag cementations materials. The optimal mechanical properties of alkali steel slag cementations materials were characterized by XRD, FTIR and SEM. The results show that When Na2SiO3 amount is 11.25 g, NaOH amount is 4.50 g and Ca(OH)2 amount is 6.75 g, alkali steel slag cementations materials’ the mechanical property is the best. Na2SiO3 has significant effect on 7 d compressive strength of alkali steel slag cementations materials, NaOH has significant effect on 3 d compressive strength of alkali steel slag cementations materials, Ca(OH)2 has significant effect on 28 d compressive strength of alkali steel slag cementations materials. The addition of alkali solution, such as Na2SiO3, NaOH and Ca(OH)2 causes steel slag to form stable C-S-H gel and zeolite.