Abstract: ObjectiveThe present study explored the pathogenicity and epidemiology characters of porcine circovi-rus type 3(PCV3)in Guangxi in order to provide the references for prevention and control of PCV3.MethodPCV3 were detected by PCR from epidemic materials of piglets died from diarrhoea. Homology modeling was conducted on its only structural protein(Cap),and phylogenetic tree was constructed. Signal peptide,glycosylation site and cell B epitope of Cap protein of PCV3 were redicteded on-line(http://www.cbs.dtu.dk/services/).ResultEpidemic materials of piglets died from diarrhoea was positive for PCV3. Its PCR amplification products was analyzed by nucleotide sequence,then gene sequence of Cap was intercepted(645 bp)and named PCV3/CN/Guangxi001/2017. PCV3/CN/Guangxi001/2017 shared 96.9%-99.4%and 98.3%-99.5%homology with Cap gene sequence of 13 PCV3 strains isolated from China and 5 PCV3 strains isolated from American respectively. However,its nucleotide sequence homology to PCV1 and PCV2 were only 43%and 45.8%,and differences in cell B epitope was obvious. Cell B epitope(92-103 aa)peculiar to PCV1,cell B epitope(69-83 aa,117-131 aa and 231-233 aa)peculiar to PCV and shared cell B epitope(156-162 aa and 179-192 aa)in PCV1 and PCV2 had no similarity.ConclusionPCV3 has been emerging in pig herd in Guangxi. Since there is no cross immunity between PCV2 and PCV3,biosafety control measures including sterilization,insecticides,rodenticides,regu-lar monitoring and self-supportive should be performed in pig farm to prevent outbreak of PCV3.