NOVELTY - Methyl-6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-8-carboxylate is added, and dried to obtain 6-chloro-4-methyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazine-8-carboxylic acid. 6-Chloro-4-methyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazine-8-carboxylic acid, 3-aminoquinuclidine hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-hydroxybenzotriazole, and triethylamine are mixed, sodium bicarbonate solution is added and organic phase is dried to obtain intermediate. Salt is added to intermediate, and recrystallized to obtain Azasetron hydrochloride.    USE - Preparation of Azasetron hydrochloride (claimed).    ADVANTAGE - The method provides Azasetron hydrochloride with high yield without using toxic solvent within a short period of time, under mild reaction conditions, by simple and environmentally-friendly process.    DETAILED DESCRIPTION - An alkali is dissolved in water to obtain alkali solution. Organic solvent is added, cooled and stirred to 20-25 degrees C. Methyl-6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-8-carboxylate is added, stirred, cooled, pH of the resulting mixture is adjusted to 1-2 using dilute hydrochloric acid, filtered and dried to obtain 6-chloro-4-methyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazine-8-carboxylic acid. 6-Chloro-4-methyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazine-8-carboxylic acid, 3-aminoquinuclidine hydrochloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-hydroxybenzotriazole, and triethylamine are mixed in a ratio of 1:1.05-1.2:1.05-1.2:1.05-1.2:2-3, dimethylformamide is added, and stirred at room temperature overnight. Saturated aqueous sodium bicarbonate solution is added to resulting mixture, extracted with ethyl acetate, organic phase is dried and concentrated to obtain intermediate. Salt is added to intermediate, salt-forming reaction is carried out, concentrated hydrochloric acid is dripped in the resulting mixture, pH is adjusted to 1-2, cooled to 0-5 degrees C, filtered and recrystallized to obtain Azasetron hydrochloride. The volume ratio of organic solvent and water is 1:1-1:3. The ratio of methyl-6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-8-carboxylate and alkali is 1:2-1:5.