Abstract: The present authors made multiple stratigraphic division of tectonic layers and lithostratigraphic study for the Cenozoic of the Qingdong Sag using the materials of lithology， well logging， seismdata， palaeobiology and regional geology.The Cenozoic in the study area can be divided into two tectonic layers: the Paleogene and the Neogene to Quaternary. The Paleogene comprises Kongdian Formation， Sha-4 Member， Sha-3 Member， Sha-2 Member from bottom to top and without Sha-1 Member and Dongying Formation. The development characteristics of strata in the Qingdong Sag are similar to the Dongying Sag except the incompleteness in vertical stratigraphic succession. Combining with drilling calibration and interpretation of seismic cross sections， remnant strata thickness isograms of four tectonic sub-layers in the Paleogene were drawn and the distribution characteristics of these strata were analyzed. The analysis shows that the thickness and distribution orientation of the remnant strata changed greatly and regularly which reflects the differences of basin sedimentary filling and tectonic evolution in different geological times. The possible causes of absence of Sha-1 Member and Dongying Formation in the Qingdong Sag were preliminarily discussed: The migration of the mantle plume high spot from the southern part of the Bohai Bay Basin towards the Bohai Sea in the Cenozoic might result in absence of sedimentation in this area in the late Paleogene. It could be proposed that the Qingdong Sag was uplifted and subjected to erosion in the period of Sha-1 Member and Dongying Formation according to the fact that the material source in the northern part of the Kendong area was derived from the southern part during this period.