Abstract: The techniques of gas chromatography(GC) and gas chromatography-mass spectrometry(GC-MS) are adopted to study the characteristics of light hydrocarbon and diamondoids from TC1 well in Tuquan Basin, which can help reveal the parent material type, depositional environment, maturity and other geochemical and geological information of crude oil. The obvious superiority of pristane content to phytane (Pr/Ph=3.17) of the oil from TC1 well indicates that the source rock was deposited in a relatively oxidizing environment. The discrimination diagram shows that the parent material belongs to Ⅱ₂-Ⅲ type, with methyl cyclohexane (MCH) index of 46%, cyclohexane (CH) index of 25% and predominant 3,4-DMD relative amount of 48% in 2 methyl adamantane. With the data of heptane(IH) index(27.6%), isoheptane(Ⅱ) index(33%), IMA (0.63) and IMD (0.38), the Ro value can be calculated to be 1.2%, revealing that the oil is in mature-highly mature stage. Combined with the previous research data, the crude oil from TC1 well is deduced to generate in the mudstone of Middle Jurassic Wanbao Formation.