Abstract： Objective To determine risk factors in nosocomial infection of trauma patients during intensive care unit stay. Methods A retrospective study was carried out. A total of 1103 trauma patients admitted to the intensive care unit of five tertiary hospitals in Zhejiang Province in 2009 were reviewed. Demographic data, injury severity score and other variables related to the trauma services were collected. Univariate and multivariate analysis were processed to identify the independent risk factors of nosocomial infection in trauma patients during stay in intensive care unit. Results Overall, 171 patients( 15.5% )developed nosocomial infection during ICU stay. Of 1103 patients, 157 patients (14.2% ) died, and the 59 fatal patients were from infection group. The mortality rate in infection group was 34.7% , which was significantly higher than that in non - infection group (10.5% ). The independent risk factors of nosocomial infection in all the patients determined by using multivariate analysis included central venous monitoring, mechanical ventilation, age ≥65, the length of ICU stay > 14 days and injury severity score ≥ 16. For the severe trauma patients, central venous monitoring, mechanical ventilation, the length of ICU stay > 14 days were independent risk factors of nonsocomial infection. Conclusions The severity of injury, age, the length of ICU stay and invasive procedures were related to the nosocomial infection. To standardize the invasive procedures and to reduce the length of ICU stay may decrease the infection rate of trauma patients.