The invention discloses a synthetic process of a chiral drug (S)-alpha-ethyl-2-oxo-pyrrolidine acetamide (levetiracetam) intermediate (S)-(+)-2-aminobutanamide hydrochloride which has anti-epileptic function. The synthetic process comprises the following steps: performing condensation on acetone cyanohydrins and n-propanal as initial raw materials in the presence of a catalyst to obtain 2-hydroxybutyronitrile; then carrying out a reaction with ammonia to obtain 2-amino butyronitrile; then carrying out hydrolysis to obtain 2-aminobutanamide; then splitting and salifying the 2-aminobutanamide to obtain a target product. The synthetic process is high in yield, the raw materials are low in price and are easily purchased on a large scale, and the synthetic process overcomes the defects that several existing processes need highly toxic and highly polluting raw materials and is simple in process operation and low in cost. Mother liquor after splitting is further racemized and split and is recycled repeatedly, so that the synthetic process is suitable for industrial production.