The Yanchang formation(Triassic) in the Ordos basin is the reservoir sandstone of the low porosity and low permeability.How has the hydrocarbon produced by the source of the Member 7 migrated to compact reservoir? What are the dynamic power and pathways for migration? These questions constitute long-term focuses.The article has adopted the methods of compaction research and palaeohydrodynamic modeling.Overpressure of Member 1 to 6 of Yanchang Formation has been resumed.Distributions and evolution of petrole.