Abstract: In order to study the functional characteristics and flavor characteristics of lactic acid bacteria fermentation of mung bean powder, Lactobacillus plantarum (LP90), Lactobacillus casei (LC89) and Lactobacillus acidophilus (LA85) were respectively used to ferment mung bean powder at different times. The functional characteristics and flavor characteristics of lactic acid bacteria fermented mung bean powder were studied, and the differences of pH value, total titrable acid (TTA), free total phenol, flavonoid, anti-nutrient factor content and antioxidant capacity of different lactic acid bacteria fermented mung bean powder were compared. The flavor was extracted by headspace solid phase microextraction and identified by gas chromatography-mass spectrometry. The results showed that compared with LC89 and LA85, LP90 showed better fermentation performance and higher content of TTA. After 24 h fermentation, the pH value of LP90 decreased the most (to 4), the TTA content increased the most (1.43 times), and the number of viable bacteria increased the most. Compared with the unfermented group (LBF), the content of free total phenols and flavonoids in LP90 after 24 h fermentation were significantly increased (P<0.05), the content of condensed tannin and phytic acid were significantly decreased (P<0.05), the antioxidant capacity was significantly increased (P<0.05). A total of 77 volatile compounds were identified by gas chromatography-mass spectrometry. Compared with the 35 flavor substances of unfermented mung bean flour (LBF), 16 and 26 new compounds were found during the fermentation of LP90, LC89 and LA85, respectively. The variety of flavor substances of LP90 fermented mung bean flour was richer than that of LC89 and LA85. Lactic acid bacteria fermentation enriched the types of volatile flavor compounds, and reduced the undesirable flavor of hexanol, octanal, nonal, heptanal and 1-octene-3-alcohol. The types of volatile flavor compounds in LP90 fermented mung bean powder were more than those of LC89 and LA85 fermented mung bean powder. In conclusion, LP90 fermentation can better improve the biological function and flavor characteristics of mung bean powder.