Abstract: Sulfates are a sort of ordinary minerals in the supergene and endogenetic geological environment. They are among the few minerals that show mass independent fractionation of oxygen isotopes. The oxygen isotopic compositions and mass independent fractionation of sulfates can provide useful information for their formation conditions, reveal special processes that can not be acquired by element concentration or single isotope ratio measurements. This is a frontier and hot topic for isotope geochemistry study in the world. Because analytical techniques of oxygen isotopes in sulfates are very complicated, this method was not established until now in China. A traditional BrF5 fluorination method for oxygen isotope measurement of BaSO4 was established recently in our lab. The separation and purification processes for BaSO4 from sulfate-bearing samples are described in this paper. The BrF5 experimental equipment, purification technique of reagent BrF5, O2 extraction preparation from sulfates and oxygen isotope measurement are introduced. The oxygen isotope compositions of an international standard of BaSO4 NBS-127, and a chemical reagent of BaSO4 were repeatedly measured. The δ^18OV-SMOW values of NBS-127 are 9.20 ± 0. 11‰ , which is the same as the published standard values. The δ^18OV-SMOW values of the chemical reagent BaSO4 are 14.64 ±0.13%o. The analysis precision of oxygen isotope ratios of BaSO4 is up to 0.13%o （1σ） , and better than 0.15 - 0.29%o （ 1 σ） reported by Wasserman （ 1992 ）.