Abstract: Based on the field observation, this paper studied in detail the geochemical characteristics of the Upper Jurassic-Lower Cretaceous bituminous vein in Tuonamu area of Qiangtang basin and discussed the bituminous kerogen origin and the forming environment. And abundant biomarkers such as n-alkanes, isoprenoids, terpanes and steranes were detected from the samples by GC and GC-MS. The carbon number of n-alkane appears as nC17 and nC18, with OEP of 0.81~1.10, Pr/nC17 of 0.73~1.36, Ph/nC18 of 0.80~1.66 and Pr/Ph of 0.64~0.90. The terpanes are dominated by pentacyclic triterpane with tricyclic terpane and gammacerane, in which C30 hopanes are dominant. The steranes are dominated by regular steranes, in which C27-C28-C29ααα20R distributes in asymmetric “V” shape. The C29ααα20S/(20S+20R) value ranges from 0.33~0.45 to 0.15~0.49, respectively. The GC-MS characteristics of saturated hydrocarbons show that the bituminous kerogen is originated from the mixed sources of phytoplankton and higher plants, revealing such a kerogen is formed in anoxic reducing environment with some salinity. The oil source correlation indicates that the bituminous vein’s biomarkers are consistent with those of the Suowa shale in terms of saturated hydrocarbons, terpanes and steranes, confirming that they have close affinity and the hydrocarbon source rocks in this area have better hydrocarbon generation potentials