The polar components of crude oils from the western Qaidam basin were analyzed by the GC-MS to determine their compositions and geochemical information. The crude oils of this region are particularly suitable for such a study since they were formed in a highly saline and strongly reducing environment and in a low-maturity stage of organic matter. Abundant fatty acids, alkanols, fatty acid glycerol monoethers, amide and stenols were identified and the glycerol monoethers were first reported for crude oils. The results suggest that they came mainly from oil source rocks. The liner compounds consist primarily of short-chain homologues and the sterols detected are predominated by C27 stenols. This reflects that algae and bacteria are the main oil-forming parent material. In particular, the presence of abundant fatty acid glycerol monoethers indicates that biological oil and fat have an important contribution to the crude oils studied. The existence of abundant unsaturated liner compounds and stenols as well as high CPI values of liner compounds shows the low maturity of the crude oils. The similarity in the distribution of both non-hydrocarbon and hydrocarbon compounds and the genetic relationship between them is discussed in this paper.