In October 2022，respiratory diseases occurred in a chicken farm in Yunnan Province. In order to find out the reason，the tissue samples collected from diseased chickens were detected by PCR for pathogens related to respiratory diseases，and the gene sequences of some positive samples were analyzed. The results showed that all the five samples were positive for the nucleic acids of Newcastle disease virus（NDV）and Omithobacterium rhinotracheale（ORT），but negative for other pathogens. The F gene of NDV in the positive samples was 100% homologous with KC844235 identified in China in 2013 and Y18898 in the United States in 2005，and belonged to Group II branch as a weak strain；the nucleotide sequence of 16S rDNA of ORT in the positive samples was in the same branch with MN023015 identified in China Mainland in 2019，DQ195253 in Taiwan in 2007 and MW298723 in Poland in 2020，fell into Group I branch，with the homology of 100%. In conclusion，co-infection with NDV and ORT was available in the farm，with little gene variation. The co-infection might worsen the diseases prevalent in the infected chickens. A reference was therefore provided for the prevention and control of co-infection with NDV and ORT.