In order to prevent and control the breakout and epidemic of diarrhea caused by Aeromonas hydrophila (AH),feces samples from 567 scattered diarrhea patients and an outbreak of collective food poisoning were investigated. Fifty one strains of AH were detected,with 18 strains harboring aerolysin gene. Epidemiological analysis of data reported in recent years revealed a tendency of increasing number of AH infection.It is reconmended that more effort should be made to investigate and monitor the AH infection.