[Background] Mycoplasma gallinaceum is a kind of mycoplasma in poultry, which occurs only in South Africa and other places, but rarely reported in China. [Objective] A mycoplasma strain was isolated from the trachea of peacock with respiratory tract disease and named Peacock20181011, to determine its taxonomic status, pathogenicity and molecular characteristics. [Methods] The newly isolated pathogenic bacterium was identified by routine microbial methods, combined with molecular biological methods and full-length genome sequences. The pathogenicity and drug sensitivity of the newly isolated pathogens were determined by pathogenicity in special pathogenic free chickens, embryos and minimal inhibitory concentration test. [Results] Through the culture, purification, morphology and staining observation of isolates, combined with biochemical tests and 16S rRNA gene sequencing, it was confirmed that Peacock20181011 belonged to Mycoplasma gallinaceum, and the 16S rRNA gene similarity to that of standard strain NCTC10183 (LR214950) was up to 99.86%, and the phylogenetic tree showed that Peacock20181011 was in the same branch of Mycoplasma gallinaceum; Artificial infection experiment showed that the fungus was not pathogenic to special pathogenic free chicken, but could cause special pathogenic free chicken embryos to develop late and the claw was curled up; minimal inhibitory concentration test showed that the bacterium was sensitive to kanamycin and florfenicol. The analysis of genome sequence showed that the bacterial length was 1 183 913 bp and the content of (G+C)mol% was 28.7%, which contained 898 coding sequences with four copies of 16S rRNA gene. [Conclusion] The existence of Mycoplasma gallinaceum in China is defined, the species of Mycoplasma in China are enriched, and the basis for prevention and control of the disease is provided.