Abstract: In order to study the effect of dosage of steel slag powder on high strength tailings concrete，the fluidity of cementitious concrete strength is conducted using steel slag powder，with specific surface area of 5 950 cm2/g，to replace the same amount of basic cementitious material，with specific surface area of 5 137 cm2/g，which is prepared by cascade grinding products with iron tailings，slag，cement clinker and natural gypsum in proportion of 40∶26∶26∶8，and then the original iron tailings as aggregate with equal quality，the concrete strength are tested.The results show that，addition of steel slag powder improved the fluidity of the system to some extent，and had a negative effect on the strength of concrete at early stage.That hydration of steel slag power acts slowly and releases sustainably made the strength of concrete increased significantly later，while the dosage of steel slag powder should not exceed 20%.The SEM analysis on the products shows that，whether mixed with steel slag powder or not，the tailings concrete has hydration products of ettringite and C-S-H gel，during the middle and later stage of the hardening process，the coordinated growth of C-S-H gel and ettringite can increase the strength of the system. 

Key words: Steel slag powder, Cementitious material, High strength tailings concrete, Fluidity, Compressive strength, Flexural strength