ObjectiveTo evaluate the epidemic characteristics of Pseudomonas aeruginosa (PA)infection in patients in ICU through typing of PA by random amplification  polymorphism DNA (RAPD). MethodsThirteen  strains of PA from lower respiratory tract in patients with nosocomialacquired pneumonia were typied by RAPD method, and were compared with antimicrobial  drugresistance spectrum typing. ResultsThirteen strains of PA were divided into two drugresistance phenotypes, type A (12 strains, 92.31%) and type B (1 strain, 7.69%), the dominant strain was type A; these strains were divided into two genotypes with RAPD typing, type Ⅰ(6 strains, 46.15%) and typeⅡ(7 strains, 53.85%).The dominant strains were  7 strains with both drugresistance type A and molecular type Ⅱ as well as 5 strains with both drugresistance type A and molecular type Ⅰ, these dominant strains were the pathogens causing PA nosocomial infection in ICU. ConclusionPA can cause  outbreak and epidemic of infection  in ICU, the epidemic strains were drugresistance type A/molecular type Ⅱ as well as drugresistance type A /molecular type Ⅰ.PA can cause multidrug resistance,RAPD typing is the ideal molecular epidemiological method for tracing source of infection.