Abstract:To investigate the effect of quercetin on the intestinal flora，photoelectric turbidimetry was used to dynamically observe the effect of quercetin on the intestinal dominant bacteria Enterococcus，Enterobacter，Lactobacillus and Bifidobacterium in vitro.An animal model of intestinal flora imbalance in mice was constructed by gavage of lincomycin hydrochloride，and the effect of quercetin on regulating intestinal flora imbalance was evaluated by in vivo experiments in mice.The results of in vitro experiments showed that quercetin had a significant effect on the proliferation of Lactobacillus in a certain concentration range（0.01，0.05，0.1 μmol/mL），beyond this range（0.5，1 μmol/mL）strongly inhibited the proliferation of Lactobacillus，each concentration of quercetin had a strong inhibitory effect on the in vitro proliferation of Enterococcus，and had no obvious inhibitory effect on Enterobacter and Bifidobacterium，but did not show enhancement.In vivo experiments showed that 200 and 400 mg/kg BW quercetin could increase the number of bifidobacteria in the intestine of mice.Quercetin could regulate intestinal flora. Key words：quercetin；intestinal flora；flora imbalance；proliferation；mice