Abstract： The biological characteristics and pathogenicity of Klebsiella oxytoca isolated from sick carrier pigeons in Gansu province were explored by morphological observations,biochemical testing,16S rRNA PCR analysis,and RNA sequencing.The drug resistance and pathogenicity of the isolated strains were studied by histopathological observation,drug susceptibility testing,and pathogenicity analysis.The livers,lungs,hearts,and other organs of the sick pigeons were bleeding.In addition,the livers were yellow and brittle,and the lungs were purulent.A Gram-negative,short,rod-shaped bacterium was successfully isolated from the sick pigeon.Pink,smooth,moist,and round colonies grew on MacConkey's agar.The result of the indigo matrix test was positive.The homology between the amplified 16S rRNA sequence and MN330093.1 was 100.00％,indicating that the sick pigeon was infected with K.oxytoca.The strain was named GS-BY-GG.K.Oxytoca GS-BY-GG was resistant to 10 drugs,including penicillin,ampicillin,and furazolidone,and sensitive to 5 others,which included florfenicol,meropenem,and gentamicin.Histopathological observation showed bleeding in multiple organs.The liver cells were irregu-larly arranged with brown-yellow pigmentation.Extensive cell necrosis and exfoliation were observed in the trachea and mucosal epithelium,with inflammatory cell infiltration in the mucosal layer.The isolates were highly pathogenic in specific pathogen-free chickens.These findings provide support for the clinical diagnosis and control of K.oxytoca GS-BY-GG.