Abstract: To investigate the influence of four types of lactic acid bacteria (LAB) on the degradation of malathion enantiomers, which included Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Lactobacillus plantarum subsp. plantarum, and Lactobacillus casei, the separation of malathion enantiomers and the enantioselective degradation were studied using an CHIRALCEL OD-H column and HPLC. Malathion in MRS medium were extracted by acetonitrile and purified with florisil SPE column. The results showed that the LABs reproduced faster in first 24 h and peaked at 36 h, then it remained steady. The pH value of medium with LABs decreased from 7 to 5 after 24 h and kept stable afterwards, while the pH value of control group remained 7. The half-lives of (±)-malathion ranged from 5.4-6.5 d and 5.1-6.3 d, respectively, and no distinct difference was observed which indicated that the degradation of malathion was not influenced by LABs.