To screen out natural compounds against Aeromonas hydrophila （A. hydrophila） infection， minimal inhibitory concentration determination， growth curves， hemolysis， Western blot， qRT-PCR and cytotoxicity assay were performed to assess the inhibitory effect of diosmetin on the expression of aerolysin secreted by A. hydrophila. The results showed that diosmetin without anti- A. hydrophila activity could inhibit the hemolytic activity of bacterial supernatants by decreasing the transcription of aerolysin gene. Moreover， live/dead staining assay showed that diosmetin could attenuate cell injury mediated by aerolysin in A549 cells. These findings demonstrated that diosmetin could reduce the pathogenicity of A. hydrophila by inhibiting the expression of aerolysin and diosmetin could be chosen as a promising candidate drug against A. hydrophila infection.