Abstract: The recent development of preparing optically active 4-chloro-3-hydroxbutanoate ester (CHBE) by biocatalysis is reviewed. The current research of racemic resolution and asymmetric reduction to prepare the optically active CHBE by biocatalysis is introduced. Several measures for controlling the stereo-selectivity of the asymmetric reduction of 4-chloro-3-oxobutanoate ester (COBE) to CHBE such as screening solvent, selection of co-substrate and additive, heat treatment of cells and so on, are presented. The prospect of industrial preparation of the optically active CHBE by biocatalysis is also discussed. biocatalysis; optical activity；4–chloro–3–hydroxbutanoate esters；racemic resolution；asymmetric reduction