Abstract: Cinnamaldehyde has good antibacterial, sterilization effect, but the features of being poorly soluble in water and easy oxidation limit its application range. In this study, cinnamaldehyde loaded nano-emulsion and hydroxypropyl（β）cyclodextrin inclusion were prepared. The determination of their antibacterial effect on 6 kinds of pathogenic bacteria-Vibrio vulnificus,Vibrio harveyi, Pseudomonas fluorescens, Aeromonas hydrophila, Edwardsiella tarda and Aeromonas sobria was applied with streptomycin as positive control. The results showed that the minimum inhibitory concentration（MIC）of cinnamaldehyde nano-emulsion against the six aquatic pathogenic bacteria mentioned above were 0.93, 2.05, 1.67, 14.88, 9.30, and 1.86 mg/mL, respectively. The minimum bactericidal concentration（MBC）were 2.40, 6.00, 1.86, 16.00, 10.23 and 5.00 mg/mL, respectively. The antibacterial effect of cinnamaldehyde nano-emulsion was significantly better than that of cinnamaldehyde hydroxypropyl（β）cyclodextrin inclusion. Conclusion: compared with cinnamaldehyde hydroxypropyl（β）cyclodextrin inclusion, cinnamaldehyde nano-emulsion has higher drug loading rate and better antibacterial activity against pathogenic bacteria. Although the antibacterial and bactericidal activity of the two formulations against pathogenic bacteria is much lower than that of streptomycin, they still have potential application prospects in aquaculture.

Key words: cinnamaldehyde, nano emulsion, minimum inhibitory concentration, minimum bactericidal concentration, aquatic pathogenic bacteria