The invention discloses a concrete with strength grade of C70 for composite structure of steel reinforced concrete. Mixed proportion of the concrete is that cement: coarse: aggregate: fine aggregate: water: effective water reducer: silica fume: fly ash is 400:576:1224:148:8:30:120. Component unit is Kg/m3. The concrete is in good mechanical properties (comprising strength, plastic and bond behavior between section steel and concrete), excellent in working performance, good in durability and relatively lower in cost, and is suitable for the composite structure of steel reinforced concrete. Theuse of the concrete reduces construction procedures, saves steel, improves construction efficiency and has remarkable economic benefit.