Oil and gas reservoirs in western Qaidam basin are often associated with faulted structures. In the southern part of western Qaidam basin, several hydrocarbon accumulation zones are distributed along the faulted zones, such as Shaxi-Gas-Youshashan, Yuejin No. 2-Yuedong and Wunan-Lucaotan hydrocarbon accumulation zones. Structural-stratigraphic-lithologic composite oil and gas reservoirs controlled by faulted nose-like structures are distributed along Chaixi and other faults. in the foothill belt of the Altun Mountain in the west. Structural-fractured reservoirs, including Youquanzi, Kaitemilite, Nanyishan and Jiandingshan, are distributed along Yingbei, Nanyishan and Jiandingshan faults in the north. The formation of faults in western Qaidam basin has been related to the Meso-Cenozoic intense compressional and strike slip movements in Altun and Kunlun mountains. The faults are mainly of reverse and strike slip faults, with a few synsedimentary normal, decolle-ment and reversed faults. The fault trends include mainly NE, NW and nearly N-S. Horizontally, the faults appear as parallel, en echelon, oblique-crossing, orthogonal, reverse"S", lenticular and divergent fault complexes. Vertically, they are combined in the form of imbricated, thrusted and flower-like fault complexes. The structural reservoirs formed by the thrust type and orthogonal and oblique-crossing fault complexes are best developed. Faults have not only controlled the distribution of hydrocarbon-generating sags and the formation of structural traps, but have also controlled, to a certain extent, the distribution of favorable reservoir facies belts, such as river delta and fan delta facies. Large amount of fractures formed by faulting improve the poroperm characteristics of reservoirs. Laterally connected oil pools, in which hydrocarbons were generated in the source rocks above and migrated through faults and accumulated in the reservoirs below, are common in the southern part of western Oaidam basin.