Abstract: To investigate the individual and combined in vitro antibacterial activity of 6 Chinese medicine monomers (Gallic acid, Glycyrrhizic acid potassium, Phenanthro, Quercetin, Physcion, Chlorogenic acid) and 3 antibiotics (Norfloxacin, Norfloxacin, Florfenicol) on Aeromonas hydrophila and Aeromonas sobria, the antibacterial activity of all test substances on the two bacteria was detected by means of the disc diffusion method. The minimal inhibitory concentration bacterial (MIC) and the minimum bacterial concentration (MBC) were determined by the micro double dilution method. The combined antibacterial effect was investigated in the way of chessboard method. Among the 6 Chinese medicine monomers, gallic acid and quercetin showed significant antibacterial effects against Aeromonas hydrophila and Aeromonas sobria, and the inhibitory circle of these two medicines were exceeded 20 mm. MIC and MBC of gallic acid on Aeromonas hydrophila and Aeromonas sobria were both 250 g/mL. MIC and MBC of quercetin on Aeromonas hydrophila were both 500 g/mL, and 250 g/mL and 500 g/mL on Aeromonas sobria.But the other Chinese medicine monomers showed no effect against these two bacteria. Enrofloxacin, norfoxacin and florfenicol showed significantly antibacterial effect against Aeromonas hydrophila and Aeromonas sobria. The result of combined experiment showed additive inhibition effect on Aeromonas hydrophila by gallic acid with enrofloxacin, gallic acid with florfenicol, and quercetin with florfenicol. The combination of gallic acid and enrofloxacin showed synergetic inhibition effect on Aeromonas sobria. The combination of gallic acid and norfoxacin or florfenicol, quercetin and florfenicol showed additive inhibition effect on Aeromonas sobria. Gallic acid and quercetin showed significant antibacterial activity against Aeromonas hydrophilaand Aeromonas sobria. And the combination of them and enrofloxacin, norfoxacin, florfenicol had additive or synergetic inhibition effect. The combination contributes to reduce the dosage and vestigital of antibiotic in aquaculture.