NOVELTY - Preparation of (S)-4-hydroxy-2-oxo-1-pyrrolidineacetamide includes adding glycine ethyl ester hydrochloride into anhydrous diethyl ether, refrigerating, charging ammonia gas to convert glycine ethyl ester hydrochloride into glycine ethyl ester, adding into anhydrous methanol, adding sodium carbonate and ethyl (S)-4-iodo-3-hydroxybutyrate, regulating the pH and temperature, reacting, filtering, completely washing the filtrate with ethanol, concentrating, dissolving the concentrate in water, adding methylene dichloride, extracting, and concentrating the aqueous phase.    USE - Preparation of (S)-4-hydroxy-2-oxo-1-pyrrolidineacetamide (claimed).    ADVANTAGE - The method uses easily obtained raw materials at reduced amount, is environment-friendly and suitable for industrial scale production, has no pollution, reduced cost, high yield i.e. more than 36%, and mild reaction condition, and provides product having HPLC purity of more than 98.5%.    DETAILED DESCRIPTION - Preparation of (S)-4-hydroxy-2-oxo-1-pyrrolidineacetamide comprises adding glycine ethyl ester hydrochloride into anhydrous diethyl ether, refrigerating at 1 degrees C, charging ammonia gas to convert glycine ethyl ester hydrochloride into glycine ethyl ester, where the ratio of glycine ethyl ester hydrochloride, anhydrous diethyl ether, and ammonia is 1 mol:1395 ml:1.5 mol, adding the resultant into anhydrous methanol, adding sodium carbonate and ethyl (S)-4-iodo-3-hydroxybutyrate, regulating the pH at 8 and temperature at 70 degrees C, reacting for 30 hours, filtering, completely washing the filtrate with ethanol, concentrating, dissolving the concentrate in water, adding 6 times by weight (based on the weight of filtrate) methylene dichloride, extracting, concentrating the aqueous phase, using column chromatography to separate, adding 10 times by weight (based on the weight of the product) of 25 mass% ammonium hydroxide, reacting for 5 hours at 20 degrees C to obtain (S)-4-hydroxy-2-oxo-1-pyrrolidineacetamide crude product, where the mol ratio of glycine ethyl ester, sodium carbonate, and ethyl (S)-4-iodo-3-hydroxybutyrate is 1:0.5:1 and the amount of anhydrous methanol is 6 times by weight of sodium carbonate, dissolving the crude product with water at 1 g:0.6 ml ratio, passing through number 732 strongly acidic cation exchange resin and number 711 strongly basic anion exchange resin, collecting the solution, concentrating, where the ratio of crude product and strongly acidic cation exchange resin is 1 g:10 ml, recrystallizing with ethanol for the first time, and recrystallizing with mixed solvent i.e. methanol/acetone for the second time to obtain the product, where the ratio of crude product and ethanol is 1 g:1.5 ml, the ratio of crude product and methanol is 1:1, and the volume ratio of methanol and acetone is 1:2.