The invention provides a method for extracting N-acetylneuraminic acid. The method comprises the following steps thata sialic acid-containing solution with the pH being 5-7 is adjusted with sulfuric acid or perchloric acid to obtain the pH being 0.5-2, crystallizing is conducted, coarse crystals are collected, and washing and drying are conducted, wherein the content of sialic acid in the solutioncontaining sialic acid is 200-600 g/L. According to the method, organic solvents are not used, operation is easy, no environmental pollution exists, the obtained product is free of residual solvent,free of plasticizer residueand high in safety.