It is clarified in this paper that the Lower Yangtze depression is a Meso-Cenozoic rift zone formed on thebasement of the Hercynian-Indosinian foreland basins. The rift zone is divided into eastern and western sectorsand is different in northern and southern parts. The rift zone in plane combination comprises parallel.trifurcate or splitting rifts. The North Jiangsu-South Yellow Sea region represents a "drift-type" rift basinwhose deposition center migrates gradually castward. The formation mechanism and dynamic evolution of therift basin are discussed from a viewpoint of the crustal fine-structure, with evidence in geology and geophysicsand analysis results of dynamic forces given.