The formation and evolution of passive continental margins are controlled by the vertical thermal- mechanical structure of pre- rifting lithosphere.In order to investigate its effect on lithospheric breakup time, faulting styles, sizes and morphology of passive continental margins, we define 3 comprehensive indexes as accumulated lithospheric yield stress (σe), average yield stress (σt) and crust- mantle rigid layers coupling degree (Coc), and reveal the influences through geodynamic numerical modelling.According to simulations, the thermal- mechanical structure of lithosphere plays a key role in controlling its rifting duration, a stronger pre- rifting lithosphere inevitably causes a longer lasting rifting, and on this basis, the decrease of the Coc will prolong this process.For the fully coupled lithosphere (Coc=1), upper crust usually breaks first, and will form symmetric margins through a ‘pure- shear’ mode.When Coc decreases, rigid layers of upper crust and upper mantle deforms separately, and an asymmetric continental margin will form by lateral migration of the rift center.Under such circumstances, the upper mantle with a relatively limited thickness will break first, while when a thick upper mantle develops, the upper crust will break first and lead to the exhumation of mantle rocks.In addition, a low Coc is necessary to generate large- scale passive continental margin basins with a broad and gentle geometry, and the lower Coc is, the greater the migration distance of the rift center and the conjugated margins are.Thickening of the crust will lead to the decreasing of Coc, which will also enlarge the scale of continental margins.Those understandings can be verified on the central segment of South Atlantic continental margins.