Abstract: The dead time of the detector of inductively coupled plasma-mass spectrometry (ICP-MS) is 43 ns obtained by measuring Re standard solution. Since there is a liner correlation between isotopic fractionation factors of Re and Ir, Ir can be used to correct Re isotope fractionation. The test by measuring Re standard solution suggests that the relative deviations between corrected and standard values are, in most cases, less than ±0.1%. The isotopic fractionation factors of Os are proportional with the middle mass of the isotopic pairs in the ICP-MS measurement. In this study, the Os isotope ratio of the mixture of the sample and spike Os (192Os/188Os)mix, obtained by iteration method is used as the normalization value to correct the isotope fractionation of other isotope ratios of Os. The test by measuring known Os isotopic solution suggests that the relative deviations between corrected and the reference values are less than ±0.3% in most cases. The correction method for Re-Os isotope fractionation presented by this paper will improve the precision and accuracy of the Re-Os dating by using ICP-MS.