Objective To investigate the causes of a suspected outbreak of healthcare -associated infection(HAI) in deep surgical incision caused by Aeromonas hydrophila(A. hydrophila) after aortic dissection operation (Standfond A), and provide evidence for effective control of infection. Methods A. hydrophila infection occurred in 3 patients after cardiac surgery in an cardiothoracic surgery intensive care unit (ICU) from September to October 2018 were investigated, deep incision drainage pus and venous blood of patients was collected, identification and antimicrobial susceptibility testing of strains were performed, epidemiological investigation and analysis was carried out. Results A. hydrophila was isolated from deep incision drainage pus and blood of 3 patients after aortic dissection operation, all were sensitive to amikacin, but resistant to other antimicrobial agents. External duct of ventilator of patient No. 2 and surface of bed unit of patient No. 3 were also isolated A. hydrophila, antimicrobial susceptibility testing results were consistent with A. hydrophila isolated from countertop of sink in ward of patient No. 1. After taking measures, such as isolation treatment for patients, strengthening hand hygiene of health care workers(HCWs), and strict implementing contact isolation, no new case of HAI caused by A. hydrophila occurred. Conclusion This event is a suspected outbreak of HAI, environmental contamination in the vicinity of patients is a possible source of transmission.