Twenty-two oil samples and eight source rock samples collected from the Tarim Basin,NW China were geochemically analyzed to investigate the occurrence and distribution of phenylphenanthrene(PhP),phenylanthracene(PhA),and binaphthyl(BiN) isomers and methylphenanthrene(MP) isomers in oils and rock extracts with different depositional environments.Phenylphenanthrenes are present in significant abundance in Mesozoic lacustrine mudstones and related oils.The relative concentrations of PhPs are quite low or below detection limit by routine gas chromatography-mass spectrometry(GC-MS) in Ordovician oils derived from marine carbonates.The ratio of 3-PhP/3-MP was used in this study to describe the relative abundance of phenylphenanthrenes to their alkylated counterparts-methylphenanthrenes.The Ordovician oils in the Tabei Uplifthave quite low 3-PhP/3-MP ratios(<0.10),indicating their marine carbonate origin,associating with low Pr/Ph ratios(pristane/phytane),high ADBT/ADBF values(relative abundance of alkylated dibenzothiophenes to alkylated dibenzofurans),low C_(30) diahopane/C_(30)hopane ratios,and low Ts/(Ts+Tm)(18α-22,29,30-trisnorneohopane/(18α-22,29,30-trisnorneohopane+17α-22,29,30-trisnorhopane)) values.In contrast,the oils from Mesozoic and Paleogene sandstone reservoirs and related Mesozoic lacustrine mudstones have relatively higher 3-PhP/3-MP ratios(>0.10),associating with high Pr/Pli,low ADBT/ADBF.high Ts/(Ts + Tm).and C_(30) diahopane/C_(30) hopane ratios.Therefore,the occuirence of significant amounts of phenylphenanthreiies in oils typically indicates that the organic matter of the source rocks was deposited in a suboxic environment with mudstone deposition.The phenylphenanthreiies may be effective molecular markers,indicating depositional environment and lithology of source rocks. Twenty-two oil samples and eight source rock samples collected from the Tarim Basin, NW China were geochemically analyzed to investigate the occurrence and distribution of phenylphenanthrene (PhP), phenylanthracene (PhA), and binaphthyl (BiN) isomers and methylphenanthrene (MP) isomers in oils and rock extracts with different depositional environments. Phenylphenanthrenes are present in significant abundance in Mesozoic lacustrine mudstones and related oils. The relative concentrations of PhPs are quite low or below detection limit by routine gas chromatography-mass spectrometry (GC-MS) in Ordovician oils derived from marine carbonates. The ratio of 3-PhP / 3-MP was used in this study to describe the relative abundance of phenylphenanthrenes to their alkylated counterparts-methylphenanthrenes. Ordovician oils in the Tabei Uplifthave quite low 3-PhP / 3- MP ratios (<0.10), indicating their marine carbonate origin, associating with low Pr / Ph ratios (pristane / phytane), high ADBT / ADBF values ​​(relative abunda nce of alkylated dibenzothiophenes to alkylated dibenzofurans, low C 30 diahopane / C 30 hopane ratios, and low Ts / Ts + Tm 18α-22, 29, 30-trisnorneohopane / 30-trisnorneohopane + 17α-22,29,30-trisnorhopane)). Values.In contrast, the oils from Mesozoic and Paleogene sandstone reservoirs and related Mesozoic lacustrine mudstones have relatively higher 3-PhP / 3-MP ratios (> 0.10) with high Pr / Pli, low ADBT / ADBF.high Ts / (Ts + Tm) .and C_ (30) diahopane / C_ (30) hopane ratios.Therefore, the occuirence of significant amounts of phenylphenanthreiies in oils typically indicates that the organic matter of the source rocks was deposited in a suboxic environment with mudstone deposition. Phenylphenanthreiies may be effective molecular markers, indicating depositional environment and lithology of source rocks.