本发明属于化工领域,涉及到一种L-2-氧代噻唑烷-4-羧酸的制备工艺。步骤是:将反应釜氮气置换三次,并保持反应釜处于氮气保护状态,向釜中加入一定量的L-半胱氨酸盐酸盐和溶剂A;控制温度于0℃-10℃下,向反应釜中加入碱水;向反应釜中加入物料B,加完后在35℃-55℃下保温反应2-4小时;反应完毕,降温至室温,静止分相,将水相用浓盐酸调整p H至2.0-3.0;减压浓缩水相至干, The invention belongs to the chemical field and relates to a preparation process of L-2-oxothiazolidine-4-carboxylic acid. The steps are as follows: the reactor is purged with nitrogen three times, and the reactor is kept under nitrogen protection. A certain amount of L-cysteine ​​hydrochloride and solvent A are added to the kettle; the temperature is controlled at 0 ° C. to 10 ° C., Adding alkali water to the reaction kettle; adding material B to the reaction kettle, keeping the reaction at 35 ° C.-55 ° C. for 2-4 hours after completion of the reaction; completing the reaction, cooling to room temperature, standing still and adjusting the aqueous phase with concentrated hydrochloric acid p H to 2.0-3.0; the aqueous phase is concentrated under reduced pressure to dryness,