The geochemical characters of the Cambrian, Ordovician, Devonian, Carboniferous and Jurassic rock samples in the eastern Qaidam basin were investigated by means of GC-MS, GC-MS-MAT, etc. Based on saturated hydrocarbon biomarker characters and stable carbon isotope composition of individual n-alkanes, the sedimentary environment of this area were studied in detail. The results showed that in the eastern Qaidam basin, the Palaeozoic organic matters were mainly from bacteria and algae, and some Palaeozoic source rocks (mainly Carboniferous) contained terrestrial bio-inputs. Majority of these organic matters was deposited in a strongly reducing marine environment, and few of them in a transitional one. The Jurassic in some areas and some geologic period was deposited in an environment of lake beach or shallow lake (semi-deep to deep lake in local areas), not in a typical coal-forming environment; therefore, the Jurassic of the eastern Qaidam basin is of oil-generating potential.