Thermochemical sulfate reduction(TSR)causes increasing of sulfur content in the oils,reduction of oil quality,and produces a toxic and corrosive H2S which may take great adverse effect on health and equipment.Although there are several ways to identify presence of TSR in gas field,yet in the case of oil with low H2S content,it is still very difficult to identify TSR.2-thiaadamantanes is one of the most effective indicators of TSR.This paper for the first time discovers 2-thiaadamantanes in the oil from Well TZ-83 in Tarim Basin.A silver nitrate silica gel chromatography was used to enrich the oil from low 2-thiaadamantanes content to the level that GC/MS and GC/MS/MS can detect.2-thiaadamantanes were assigned by comparison of mass spectra with published data,and the fragmental ions in mass spectra were confirmed by MRM mode of GC/MS/MS.H2S gas produced in Tazhong area is thought to be gen-erated from TSR since 2-thiaadamantanes were present in the oil. Thermochemical sulfate reduction (TSR) causes increasing of sulfur content in the oils, reduction of oil quality, and produces a toxic and corrosive H2S which may take great adverse effect on health and equipment. There are several several ways to identify presence of TSR in gas field, yet in the case of oil with low H2S content, it is still very difficult to identify TSR.2-thiaadamantanes is one of the most effective indicators of TSR.This paper for the first time discovers 2-thiaadamantanes in the oil from Well TZ-83 in Tarim Basin. A silver nitrate silica gel chromatography was used to enrich the oil from low 2-thiaadamantanes content to the level that GC / MS and GC / MS / MS can detect.2-thiaadamantanes were assigned by comparison of mass spectra with published data, and the fragmental ions in mass spectra were confirmed by MRM mode of GC / MS / MS. H2S gas produced in Tazhong area is thought to be gen-erated from TSR since 2-thiaadamantanes were present in the oil.