A strain was isolated from internal organ of died porcine about 8 weeks with purulent pneumonia, arthritis, pyogenic arthritis and endocarditis in April 2007. Objectives of the study are to confirm the genus of the strain, pathopoiesis, and drug sensitivity. The mainly study methods: the first, the strain was identified by the phenotype and the characteristics of the biochemistry, sequence 16S rDNA genes of the strain was analyzed by molecular biology technology, finally animal experiment and drug sensitivity testing were done. The results of the phenotype and the characteristics of the biochemistry showed that it is greatly similar to Actinomyces hyovaginalis, 16S rRNA sequence analysis exhibited the homology achieved to 99.2% compared with group III strains of Actinomyces hyovaginalis, and the phyletic evolution analysis also indicated that it has mostly relationship with group III strains of Actinomyces hyovaginalis. Animal experiment discovered it has highly pathogenicity to Mus musculus albus; Drug sensitivity testing showed that it is hypersensitive to Erycin, Gentamicin and Amikacin. So, the result of the study confirmed that the strain is Actinomyces hyovaginalis III with the pathogenicity.