Abstract: A method of GC for the determination of optical purity of 2-chloropropionic acid with precolumn derivatization was proposed. 2-Chloropropionic acid was mixed with same volume of the derivatizing reagent thionyl chloride, and derivatized for 30 min in an ice bath. The derivative of 2-chloropropionic acid, racemate of methyl 2-chloropropionate, obtained was separated on CYCLOSIL-B chiral column at 65 ℃. The resolution of more than 2.0 was attained. The present method was used in the determination of optical putity of 2-chloropropionic acid, and the results obtained were in conformity with the theoretical values.