A strain of virus was isolated from 20 cloacal of ducks in Nanjing using SPF chicken embryos.The virus showed haemagglutination activity but not inhibited by positive sera against New castle disease virus(NDV) and egg-drop syndrome-76 virus(EDSV).HI test indicated that the isolate belonged to H9 subtype of influenza virus.The assay of intravenous pathogenicity showed that the isolate had low pathogenicity to chickens,but no pathogenicity to ducks.The study also indicated that the 5-week-mouses could be infected with morbidity and mortality.