The recent tectonic activity, in the Keshen- Kedong areas in the piedmont of the western Kunlun Mountains, is intense, and there is a very high overpressure with a pressure coefficient of 2.1 in the shallow sequences. The research and understanding of the distribution and mechanism of this overpressure is of great significance for the study of drilling engineering and hydrocarbon migration. Based on the data of measured reservoir pressures, ones estimated from mudstone and the relationship between rock mechanics and physical properties, the distribution characteristics and main control mechanism of formation pressure are analyzed, combined with fault development conditions and hydrocarbon migration history in the study area. The results show that the Paleogene- Cretaceous reservoirs form a relatively unified abnormal pressure system. The formation pressure in this system increases with a hydrostatic pressure gradient, and the reservoir pressure is greater than the neighbouring mudstone. The reservoir pressure distribution are closely related to the upward transmission of deep fluid along the open faults. Finally, the overpressures transfer by fault is estimated, and the related geological factors are discussed. The ratios of the fault transmitted pressure to the measured total overpressure in Keshen and Kedong areas are 24.2%~67.2% and 23.4%~53.7%, respectively. The difference of transferred amount between the two areas is controlled by fault development and its spatial relationship with the formation.