A method for preparing levetiracetam in a high purity comprising 1) mixing (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid (R)-α-methylbenzylamine salt with an aqueous solution of inorganic base, adding a first organic solvent to extract free (R)-α-methylbenzylamine, and collecting an aqueous layer; 2) adding an acid to adjust the aqueous layer obtained in step 1) to pH 5-9; then removing water to obtain an oil; then dissolving the oil with a second organic solvent to obtain a solution containing (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid; the acid is one of hydrochloric acid and sulfuric acid, or a combination thereof; 3) performing an esterification reaction of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid in the solution obtained in step 2), and then an ammonolysis reaction to obtain levetiracetam; preferably, the esterification reaction of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid in the solution is performed with ethyl chloroformate or methyl chloroformate; preferably, the ammonolysis reaction in step 3) is achieved by contacting with ammonia; more preferably, the ammonia is derived from liquid ammonia or an organic solution of ammonia, wherein the first organic solvent in step 1) is one selected from the group consisting of benzene, xylene, toluene, n-butyl acetate, n-hexane, n-heptane and cyclohexane, or a combination of at least two of them, preferably toluene, and wherein the second organic solvent in step 2) is one selected from the group consisting of dichloromethane, chloroform, carbon tetrachloride and 1,2-dichloroethane, or a combination of at least two of them, preferably dichloromethane. Wherein the high purity refers to a purity of 95% or more. 1) mixing (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid (R)-α-methylbenzylamine salt with an aqueous solution of inorganic base, adding a first organic solvent to extract free (R)-α-methylbenzylamine, and collecting an aqueous layer; 2) adding an acid to adjust the aqueous layer obtained in step 1) to pH 5-9; then removing water to obtain an oil; then dissolving the oil with a second organic solvent to obtain a solution containing (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid; the acid is one of hydrochloric acid and sulfuric acid, or a combination thereof; 3) performing an esterification reaction of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid in the solution obtained in step 2), and then an ammonolysis reaction to obtain levetiracetam; preferably, the esterification reaction of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid in the solution is performed with ethyl chloroformate or methyl chloroformate; preferably, the ammonolysis reaction in step 3) is achieved by contacting with ammonia; more preferably, the ammonia is derived from liquid ammonia or an organic solution of ammonia, wherein the first organic solvent in step 1) is one selected from the group consisting of benzene, xylene, toluene, n-butyl acetate, n-hexane, n-heptane and cyclohexane, or a combination of at least two of them, preferably toluene, and wherein the second organic solvent in step 2) is one selected from the group consisting of dichloromethane, chloroform, carbon tetrachloride and 1,2-dichloroethane, or a combination of at least two of them, preferably dichloromethane. Wherein the high purity refers to a purity of 95% or more. <EOS>