Abstract: In order to identify the pathogen that caused the death of sick geese in a goose farm in Nanning City, Guangxi Zhuang Autonomous Regian, and to understand its pathogenic characteristics, in this experiment, firstly, the liver, lung and other tissue disease materials of the sick and dead geese were collected, and the susceptible virus detection and bacterial isolation and identification were carried out. Then, the isolated strains were subjected to PCR amplification based on 16S rRNA gene, pathogenicity test, genetic detection of virulence factors, drug susceptibility test, and multi-site sequence typing. Finally, based on the results of multi-site sequence typing, a phylogenetic tree was constructed to analyze the genetic evolution relationship of isolated strains. The results showed that no Goose parvovirus, Duck hepatitis virus, duck Tembusu virus, Duck reovirus, Duck circovirus, avian Influenza A virus, Newcastle disease virus and other viruses were detected in the tissue samples of sick and dead geese. One strain of Citrobacter was identified by bacterial isolation and PCR amplification of 16S rRNA gene. All mice died after intraperitoneal injection of 0.5 mL of isolate solution（concentration of 4×10~8 cfu/mL） for 48 h. After autopsy, lung hemorrhage, liver congestion, spleen enlargement and bleeding and other lesions could be seen; it could cause widening of the alveolar septum in mice, filling the hepatic sinus with red blood cells, and dilation of the splenic sinus. The isolated strain contained virulence genes ompX, ureF and cfa was resistant to penicillin, cephalexin, amoxicillin, streptomycin, kanamycin, gentamicin, tetracycline, florfenicol, sulfamethoxazole, vancomycin, polymyxin, and was doxycycline, moderate resistant to cefuroxime, imipenem, and sensitive to ceftazidime, cefotaxime, amikacin, norfloxacin, ciprofloxacin, meropenem. The five housekeeping genes aspC, clpX, fadD, arcA and lysP of the isolated strain were completely matched to the alleles already in the PubMLST database, while the other two housekeeping genes dnaG and mdh were not matched. The isolated strain was most closely related to the Citrobacter strain CB00003 isolated from human cyst wounds in Europe. The results suggested that the pathogen that caused the goose death in a goose farm in Nanning City, Guangxi Zhuang Autonomous Regian was Citrobacter, which had strong virulence and belonged to a new sequence type.