The invention discloses a method for preparing D-
cycloserine through a one-pot method. The method comprises: carrying out a reaction on 3-chloro-D-
serine and
thionyl chloride in a
solvent to obtain anintermediate 3-chloro-D-alanyl
chloride hydrochloride solution; preparing a 35%
sodium hydroxide aqueous solution, cooling to a temperature of less than 0 DEG C, controlling the temperature at -5 to5 DEG C, and adding the 3-chloro-D-alanyl
chloride hydrochloride solution; uniformly stirring after completing the adding, controlling the temperature at -5 to 5 DEG C, and adding a
hydroxylamine hydrochloride solution; slowly heating to a temperature of 20-30 DEG C after the adding, and adjusting the pH value of the solution to 10.5-12.0 by adding a 35%
sodium hydroxide aqueous solution; carryingout standing liquid separation after completing the reaction; taking the water phase, and concentrating to achieve a near dry state; adding
methanol, dissolving, and filtering to obtain a
methanol solution; cooling to a temperature of -5 to 5 DEG C, and adjusting the pH value of the solution to 6.0-6.5 with a 60%
acetic acid methanol solution; and carrying out stirring
crystallization, carrying out
centrifugation,
drying the obtained wet product to obtain crude D-
cycloserine, and refining to obtain the D-
cycloserine finished product. According to the present invention, the product prepared bythe method has a
liquid phase purity of more than 99.6% and a
specific rotation of more than +110 DEG.