Objective To 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 in-fection.Methods Bacteria isolated from clinical specimens were identified by BD Phoenix automated microbiology system. Gene homology were analyzed with randomly amplified polymorphic DNA (RAPD)technique.Results Forty-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 electrophore-sis 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. Conclusion Localized 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. Gen-otyping 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.