The invention discloses a cement-free iron runner castable. The cement-free iron runner castable is composed of 58-62% of a compact corundum aggregate, 6-10% of silicon carbide, 2-3% of spherical asphalt, 1.5-6% of silicon nitride powder, 6-10% of alumina micro powder, 3-6% of silicon dioxide micro powder, 0.2-0.4% of nano carbon black, 3-8% of silicon carbide powder, 0.2-0.4% of boron carbide powder, 0.5-1% of metal aluminum powder, 0.5-1% of metal silicon powder, 0.08-0.12% of explosion-proof fibers, 0.1-0.3% of a dispersing agent and 2-8% of compact corundum powder. According to the invention, an iron runner castable system is formed by combining high-purity silicon dioxide micro-powder and aluminum oxide micro-powder, so that the purity, refractoriness and compactness of the castable reach a new height. Through high-purity, high density and the like of the system disclosed by the invention, the heat-state rupture strength, which is the index with most high-temperature representativeness, after heat is preserved by 1 hour at 1400 DEG C reaches 10 MPa or above.