Abstract: Objective By analysing the pathogen of SFTSV found in 8 cities of Liaoning province during 2009-2011,we try to find out the possible host animals and carriers of the virus.Methods IgM antibody of blood virus nucleic acid of severe fever with thrombocytopenia patients in Liaoning province during 2009-2011 was tested by eNzyme-linked immunosorbent assay(ELISA).Antigen of SFTSV in rat lung was tested by indirect immunofluorescence assay(IFA).SFTSV nucleic acid testing of tick suspension,rat lungs,and positive isolation of cell was tested by reverse transcription(RT)-PCR.The virus was isolated by VERO-E6 and identified with DNA sequencing analysis.Results IgM antibody was detected in Dalian,Dandong,Fushun,and Tieling city.Twenty rat lungs were found with SFTSV antigen,but nucleic acid of SFTSV was not detected.SFTSV nucleic acid was found in one of 20 tick suspension samples and SFTSV was isolated.Twenty-six of 148 acute phase blood samples induced cytopathic changes in VERO-E6 cells.SFTSV was identified and M segment nucleotide was sequenced.Conclusion SFTSV is a new pathogen of severe fever with thrombocytopenia syndrome fever in 4 cities of Liaoning province.SFTSV nucleic acid was not detected in possible animal rodent host and ticks may be one of the carriers.