Among 49 patients (33.1%) with HAP (35 male and 14 female), 89.8% cases were suffered from ventilator - associated pneumonia; the average age was 66.3 ± 17.6 years old; the average incubation period was 7±2.4 days; 12.7% cases had early incubation period and 87.3% cases had late incubation period; Many risk factors related to HAP after abdominal operation admitted at ICU consisted of age > 60 years old, hypertension, chronic obstructive pulmonary disease, liver failure, cardiac failure, renal failure, diabetes, emergency operation, operation > 2 times, tracheal intubation, repeat tracheal intubation, mechanical ventilation, tracheotomy, gastric intubation, sputum aspiration, and sedative use significantly (p<0.05).