Abstract: Rhus chinensis Mill., Rheum palmatum Linn., Rhizoma polygoni Cuspidati, Punica granatum Linn., Scutellaria Baicalensis georgi and Coptis chinensis Franch, were first ground into superfine powder respectively. Then they were mixed one by one based on chessboard experimental method to get nineteen kinds of compounds of Chinese herbs. To study antibacterial activity of the compounds, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of single drug and the compounds against five strains of pathogenic Aeromonas from eels were measured with agar dilution method. The results showed that six kinds of Chinese herbs had antibacterial effect at certain extent on the five bacteria. RCM had the best antibacterial activity, followed by PGL and RPL, CCF had the worst antibacterial activity. Fifteen double combinations had synergism antibacterial effects against pathogenic bacteria at different extend, and antibacterial activity of almost all compounds increased, whose inhibitory concentration reduced at least 39%. The ratios of FIC≤1 and FIC≤0.5 to all FIC were 85.7% and 23.3% respectively. Four kinds of triple combinations had synergism antibacterial effects against five strains of pathogenic Aeromonas significant synergistic inhibitory effect, whose inhibitory concentration reduced at least 80%. But FIC of prescription HC14 on the four pathogens was greater than two, which occurred the phenomenon of mutual antagonism, and resulted in antimicrobial activity reduce. The study also indicated that the rational use of Chinese herbal compounds could not only increase drug antimicrobial efficacy, but also could significantly reduce the concentration of Chinese herbs in the compounds. Therefore, the environmental pollution and the resistance to drug caused by medicaments also could be reduced greatly. Obviously, the results obtained from this study can lay a theoretical basis for exploitation of efficient, lower residual, safe and environmental friendly drugs against pathogenic bacteria from fishes.