OBJECTIVE To study the causes of hospital acquired infections in the general hospitals and provide the reliable evidence to prevent and control the hospital acquired infections.METHODS By means of retrospective investigation,we observed 78829 patients with hospital acquired infections collected from May 2004 to Apr 2006 in our hospital.RESULTS The hospital acquired infection rate was 3.07%,the most cases were with respiratory infection,accounted for 59.07%,mainly with G-bacteria accounted for 49.73% and caused by primary malignancy,accounted for 18.05%.CONCLUSIONS The high risk factors of hospital acquired infections are immunosuppression,more invasive examinations and treatments and long-term using antibiotics.