To study the proliferation and location of hantaan virus (HV) in gamasid mites and chigger mites.HV RNA in gamasid mites and chigger mites were detected by reverse transcription, polymerase chain reaction (RT- PCR) and in situ hybridization.The smallest quantity of mite from which HV RNA could be detected was 5 mites group. The titers of -and proliferated in mites HV RNA could be found in ovary cells and dug cells of gamasid mites and chigger mites by in situ hybridization.The results showed that HV could be trans-stadially transmitted and proliferated in mites, and HV always located in ovary and dug organs of mites. These results provide direct evidence at molecular level for the role of gamasid mites and chigger mites as vectors in transmission of HV.