Abstract: The change ratio of geochemical parameters was proposed and applied in the Bonan Subsag, Zhanhua Sagto quantitatively identify the migration dynamics and patterns of petroleum in overpressured basins. Based on oil source correlation, migration pathway recognition and pressure distribution, the method of the change ratios of geochemical parameters was selected and calculated to identify the range of overpressure-driven, buoyancy-driven or complex driven oil reservoirs. Migration dynamics, patterns and function boundariesin the process of hydrocarbon migration can be determined. This method can quantitatively characterize and recognize hydrocarbon migration patterns. However, influenced by the changing characteristics of parameters, it is applicable to identify the patterns of hydrocarbon migration for the same origin, the same path and the same period. Affected by differential structural background, hydrocarbon propertiesand migration pathway,the determining boundary of the change ratio of geochemical parameters has differentiation and regional specificityin application.