Abstract: Based on coring data,logging data and analysis results,combined with the seismic forward modeling technology and wave impedance properties,the research on reservoir characteristics of bottom lower member from Minghuazhen Formation and the sedimentary model in southern Bohai Sea were discussed.The results indicated the mixed river sedimentary model was for bottom lower member,with characteristics of thin sand bodies,fast lateral change and mixed plane shape,and it could be considered as a transitional sedimentation type from braided river of Guantao formation to shallow water delta of the middle part of lower member of Minghuazhen Formation.Compared with braided river and meandering river,the mixed river had little topographic slope,weaker flowing dynamics and stronger channel stability.Different river hydrodynamic intensity determined different lithologic combination,sand body morphology and structure characteristics of the deposit.It was difficult to describe the thin sand bodies of the bottom lower member from Minghuazhen Formation.By analyzing seismic attributes and in combination of fault characteristics and the channel direction,the oil boundary was found and delineated,which provided a more reliable basis for later development plan..