Abstract: The base fault pattern of the Qaidam Basin determined the basin's tectonic evolution and its sedimentary development, and resulted in 3 distinguishing fault structure systems of the north edge, the middle and the Kunbai.The north-edge fault system shows a anti-S shape in plane, and in section the fault system displays a series of reverse fault belts having a south-dip direction and lining many syndepositional structures like steps controlled by the fault system.They are effected by Qilan mountain tectonic stress field on the north.The Kunbei fault system are composed of some press fault-depressions and fault-step belts in the south of the basin.Its formation is controlled by Kunlun mountain tectonic stress field on the south.The middle fault system has a common structure of a swelling press form both side faults as its important feature.It is effected by two stress fields of Qilan mountain and Kunlun mountain in the same period.The faults play very important roles in hydrocarbon accumulation and distribution.It was pointed out that future hydrocarbon exploration in the basin is the middle part-middle fault structure system according to the fault controlling law on hydrocarbon accumulation in the basin and its petroleum geologic conditions, especially the Ebonang-Yikeyawuru, Yahu-Taijnail tectonic belts and middle-south swelling region.Petroleum exploration of the Qaidam Basin may make a huge breaktrough in these areas.