The invention relates to the field of refractory materials and concretely provides a composition for preparing a molten aluminum runner. The composition comprises an aggregate, a filler, a binder and a dispersant. The aggregate comprises one or more of fused silica particles, electro-fused corundum particles and electro-fused mullite particles. The filler contains 20-100% by weight of a first filler. The first filler is fly ash. The invention provides a molten aluminum runner and a preparation method thereof. The preparation method comprises mixing the composition and water to obtain a castable material, pouring the castable material into a mold, carrying out molding, and carrying out maintenance, demolding, drying and calcining. The used composition is the composition provided by the invention. The volume density of the molten aluminum runner is 1.5-2.5 g/cm<3>, the apparent porosity is 10-40%, the compressive strength is 20-80MPa and the flexural strength is 5-20MPa. The preparation method and formula are environmentally friendly, realize a low cost, effectively utilize the industrial solid wastes, and improve the use performances of the molten aluminum runner.