Preparation method of S-2-aminobutanamide

The invention provides a preparation method of S-2-aminobutanamide, comprising the steps of 1), reacting hydrogen cyanide, ammonia and n-propanal as materials to obtain 2-aminobutanenitrile; 2), separating a reacted liquid of step 1) by means of extraction to obtain an oil phase and a water phase, adding a catalyst and an alkali solution into the oil phase to carrying out hydrolysis, and reacting to obtain hydrolysate; 3), adding an acid or acid aqueous solution into the hydrolysate of step 2), separating to obtain an oil phase and a water phase, and separating the water phase to obtain S-2-aminobutanamide. The hydrogen cyanide, n-propanal and ammonia are reacted as materials to synthesize 2-aminobutanenitrile, the 2-aminobutanenitrile is hydrolyzed to directly obtain a target product, little byproducts are produced in reaction, and the content of the target product is high; little waste water and waste gas are produced in reaction, zero residue is produced, and there is no mass waste salts produced in the so