The invention discloses a carbon-free ladle brick and a preparation method thereof. The carbon-free ladle brick is prepared by using bauxite chamotte, a corundum raw material, magnesium oxide and alumina micro powder as main raw materials, adding iron oxide, a magnesium chloride solution, sodium hexametaphosphate and canary dextrin, mixing the above-mentioned materials by using special procedures, storing an obtained mixed for 30 min, carrying out compression molding and drying the mixture at a temperature of 200 DEG C for 24 h. According to the invention, iron oxide and alumina micro powder are enabled to exist in gaps between aggregate and powder and form hercynite with a low thermal expansion coefficient at a medium-high temperature, and no excess iron oxide enters into a matrix, which enables the ladle brick to have good high temperature stability and anti-stripping performance; therefore, the problem that molten steel carburetting caused by high temperature melting loss of a refractory brick influences smelting quality is overcome, and the prepared carbon-free ladle brick has excellent performances of high strength, washing resistance, a long service life, etc.