Objective To investigate the nosocomial infection (NI) in patients in ICU, and analyse the risk factors and preventive measures. Methods The clinical data of all patients who were hospitalized between January 1, 2000 and December 31, 2002 were surveyed retrospectively. Results NI in patients in ICU was 19.69%, the case prevalence rate was 28.19%, the infection often occurred in patients with cerebral hemorrhage, cerebral infarction, cerebral laceration and contusion; lower respiratory tract infection was the most common infection (60.32%), the next was bacteremia; Gram-negative bacteria was the main pathogens causing NI (67.83%), most of which was Pseudomonas aeruginosa (34.78%), followed by fungi (17.39%). Conclusion The NI rate of ICU is higher than that of the other departments, the risk factors depend on the severity of underlying diseases, patients immunity status, invasive procedure and the quality of disinfection and sterilization.