Abstract:Five kinds of Lactic acid bacteria isolated and identified by our research team were selected to ferment citrus peel.The levels of different kinds of flavonoid （naringin，tangeretin，rutin，hyperin，quercetin，luteolin，naringenin，apigenin and isorhamnetin）during fermentation process were determined by liquid chromatograph-mass spectrometer（LC-MS），also total amounts of flavonoid were calculated.The strain which produces the highest content of total flavonoids was chosen for further research. In order to optimize the total flavonoids contents from fermentation process，the effects of carbon source addition，inoculum concentration，incubation time，liquid-solid ratio and their interactions have been studied in this paper with Box-Behnken design. The results showed that the fermentation gained from Lactobacillus casei （5A-1-1）had the highest contents of flavonoid among different strains，the optimal fermentation conditions were：3.25% of carbon source addition，2.97%of inoculum concentration，2 days of incubation time and 1 ∶4 mass ratio of the solid-liquid mass ratio.Under these conditions，the total flavonoid from fermentation was（0.208 667±0.008）mg/g which was similar to that predicted.Therefore，using the response surface methodology was reliable.