Abstract: For production of functional fermented soymilk, one strain was selected from one hundred lactic acid bacteria isolates based on their capacities to hydrolyze isoflavone glucosides to aglycones by high performance liquid chromatography (HPLC) . Based on the biochemistry and genetic characteristics analysis, the strain was classified as Lactobacillus plantarum. Fermentation conditions including fermentation time, temperature and inoculum amount were optimized by one-factor-at-a-time and response surface methodology (RSM) . The optimum fermentation condition as follows:fermentation for 17 h at 45℃ with inoculation amount of 5%, while the soy isoflavone aglycones production was 132.814μg/mL.