By 2D gas chromatography and time-of-flight mass spectrometry (GC×GC-TOFMS), 81 ethanodiamondoids with 1-3 cages were detected quantitatively in Ordovician crude oil from well SN1, Shuntuoguole area, Tarim Basin, including 47 ethanoadamantanes with total content of 27 594.0 μg/g, 32 ethanodiamantanes with total content of 4 415.1 μg/g, and 2 ethanotriamantanes with total content of 16.8 μg/g. The template of 2D chromatogram retention index of diamondoids-ethanodiamondoids was constructed. The results demonstrated that the position of retention time of diamondoids and ethanodiamondoids has the following relationship, namely, adamantanes < ethanoadamantanes < diamantanes < ethanodiamantanes < triadamantanes < ethanotriamantanes < tetradamantanes. Quantitative analytical result of ethanoadamantanes as saturated hydrocarbons with the highest thermal stability in crude oil, is expected to provide new indexes for secondary reservoir reconstruction, i.e. crude oil cracking and thermochemical sulfate reduction (TSR).