In order to clarify the time- space evolution of tectonic activities during the ocean continental transition, we analyse and interpret 2 long seismic lines which across the conjugate margin of South China Sea. Four first order interfaces have been recognized in the ocean continental transition of SCS: Tb, SD, PD and Bi. These 4 first order horizons separated the basins on continental margin into different proto- basins: the early rifted basin (Tb- SD), the later detachment basin (SD- PD), and the transfer basin (PD- Bi). Based on the comparison of syn- tectonic sequences in different domains in one seismic line, the tectonic activities from continent to ocean. As inferred from comparison, the syn- tectonic sequences in same domain between different lines, the tectonic activities get younger along the seafloor spreading direction. Thus, during the seafloor spreading stage, the lithosphere extension deformation propagated not only from continent to ocean, but also along the seafloor spreading direction.