Abstract: The effect of extraction solvent，acetic acid concentration，extraction temperature，time and solid-liquid ratio（g/mL）on the extraction rate of flavonoids from the water chestnut peel was studied. The optimized parameters was obstained with the single factor and orthogonal design. The results showed that 75% acetic acid concentration，70℃，solid-liquid ratio 1∶14 and 6 h，the extraction rate of flavonoids reached 1. 56%. The antibacterial effect of flavonoids in the water chestnut peel to Escherichia coli，Bacillus subtilis，Staphyloccocus aureus and Pseudomonas aeruginosa were measured. The results showed that extracts of the water chestnut peel had the antibacterial effect to the 4 species germs，but the amount of flavonoids content has no obvious correlation with the antibacterial effect，It can be inferred that the antibacterial substance in extractive is not only flavonoids. The extracting flavonoids and antibacterial effect to 4 species germs had no linear relationship when the flavonoids extracted on different temperature ranged from 50 ℃ to 80 ℃.

Key words: water chestnut peel, flavonoids, extraction, antibacterial effect