Abstract: The present paper deals, in terms of well logs and analytical results, with the source rocks, reservoir rocks, cap rocks, hydrocarbon accumulation and migration, trap formation and distribution in the Yanchang Formation, Majiatan Oil Field, Ordos Basin. The Chang-7 oil measures occur as the main source rocks, the Chang-10 oil measures as main reservoir rocks, and the topmost mudstones of the Chang-10 oil measures as the main cap rocks in the Majiatan Oil Field. The fault-controlled oil traps act as the main traps. The fault-controlled oil reservoirs are believed to be the main oil reservoir type in this region, and the faults appear as the good pathways for the hydrocarbon migration. The prospect areas include the Majiatan, Gufengzhuang and Ma'erzhuang-Yujialiang zones in the Majiatan Oil Field.