ObjectiveTo study the risk factors of Pseudomonas aeruginosa （PA） infection and homology of PA isolated from nasopharyngeal carcinoma patients undergoing  radiotherapy, and prevent and control the spread of infection.MethodsBacteria isolated from clinical specimens were identified by BD Phoenix automated microbiology system. Gene homology were analyzed with randomly amplified polymorphic DNA (RAPD) technique.ResultsFortynine strains of PA were mainly isolated from 43 nasopharyngeal carcinoma patients, the major specimens were nasopharyngeal swab (46.94%), sputum(32.65%), and oral secretion (10.20%).All these strains were amplified 46 electrophoresis diagrams, and 19 genotypes were identified. The highly homologous genotypes of type H and J strains were mainly isolated from patients in the second section (57.14%,4/7） and fourth section (60.00%,3/5） of radiotherapy department respectively.  ConclusionLocalized epidemic of highly homologous PA exists in different sections of ward, transfer of patients between different sections is the risk factor for homology PA infection/colonization. Genotyping technique  such as RAPD for analyzing the homology of pathogenic bacteria in healthcareassociated infection has important value in preventing and control Ling infection  spread.