The invention discloses a converter slag-stopping inner nozzle brick and a preparation method thereof. The brick is prepared from, by weight, 50%-60% of plate-shaped corundum particles, 1%-16% of fused spinel particles, 10%-20% of fused corundum powder, 2%-18% of fused spinel powder, 1%-6% of alpha-Al2O3 micro powder, 0.3%-3.0% of black silicon carbide powder, 0.3%-3.0% of metallic silicon powder, 1%-2% of sialon powder, 2%-6% of clay powder, 0.3%-3.0% of -195C graphite and resin binders, wherein the resin binders account for 3%-5% of the total mass of all other components. The converter slag-stopping inner nozzle brick has the advantages that the sialon powder is added, air holes which are evenly distributed and have superfine sizes are formed in the product use process, the elastic strain energy can be well absorbed and dissipated, the destructive effect of thermal stress on materials is alleviated, the thermal shock resistance of the inner nozzle brick is improved, the anti-stripping property of the inner nozzle brick and the resistance of the inner nozzle brick to slags and erosion of molten steel are improved, the service life is prolonged, and potential safety hazards are eliminated.