Abstract: The isotopic ratios of rhenium in three rhenium ribbon materials with different origins have been measured by thermal ionization mass spectrometry. The average ~(185)Re/~(187)Re ratio for three samples was determined to be 0.59721±0.00008(2SD) with a preeision of 0.013％ (95％ confidence limits), yielding a new value of the atomic weight of rhenium is 186.20693(6).