Abstract: In order to study the hydrocarbon differential accumulation of the foreland basins in the western South America and its controlling factors, we collected over 4 400 data of 14 foreland basins within IHS2009 database. Several conclusions were made as followed. (1) The foreland basins have distinct segmental accumulation characters. Hydrocarbon mainly accumulated in the north, accounting for 85% of total recoverable reserve, while in the center and south, only 6.9% and 8.1%, respectively. Vertically, hydrocarbon mainly distributes in the Upper Cretaceous and Tertiary reservoirs in the north, below Jurassic in the center, and in Jurassic and Cretaceous in the south. (2) The segmental features of petroleum geology controlled the differential accumulation of hydrocarbon. The segmental development of source rocks determined the plane enrichment of oil and gas. The segmental development of reservoirs and cap rocks controlled the vertical distribution of hydrocarbon.