The invention relates to a carbon-silicon-tungsten-yttrium lamellar structure high-niobium titanium-aluminum alloy and a preparation method thereof. The alloy belongs to a gamma-TiAl alloy and comprises 45.0-48.0% of Al, 5.0-8.0% of Nb, 0.5-1% of C, 0.1-0.5% of Si, 1.0-2.0% of W, 0.1-0.5% of Y, and the balance of Ti. The preparation method comprises the steps of preparing a button ingot through electric arc melting, casting a cylindrical test bar through suspension smelting, conducting directional solidification on the test bar by an optical float-zone method, and obtaining a lamellar structure high-niobium titanium-aluminum alloy sample. Compared with the common titanium-aluminum alloy, grains of the alloy can be further refined, the strength and rigidity of the alloy can be further improved, and the alloy has good oxidation resistance and creep resistance, and can overcome the disadvantages of poorer room-temperature brittleness and room-temperature ductility. In addition, as the optical float-zone method is adopted for the directional solidification, an oriented lamellar structure can be obtained, properties of the alloy, such as fracture toughness, creeping strength and room-temperature ductility, can be improved greatly, and the alloy has the advantages that no crucible is required, no pollution is caused, and the growth speed is high.