Abstract: A self-made electrothermal vaporization (ETV) device was used to solve the isobaric interference in the isotope ratio analysis by ICP-MS. As a sampling method used in ICP-MS, ETV was used about twenty years and performed many merits. One of these merits is that it can separate the matrix of sample online according to the different evaporation rate of different element or compound on the filament of ETV. By this character, the isotope ratio of ¹⁷⁶Lu/¹⁷⁵Lu , as a example, was determined under the isobaric interference of ¹⁷⁶Yb by ETV-ICP-MS .