Abstract: In the case of no well,by using ancient environment and3 D seismic data in surrounding areas,with numerical simulation software on sedimentation,a fine study on the formation process of the sublacustrine fan and space distribution of Dong-II member of Liaozhong sag in Bohai sea waters has been carried out.Lower Dong-II member in the research area can be divided into a third-order sequence and 3 systems tracts;the lacustrine level curve presents pulse wave changes and the main source is from two directions in the east side and north side.Through structure diagrams of various system tracts,with the software to restore the ancient landscape and the ancient structure,the relative real sedimentary background has been obtained.By using these geological parameters,the numerical simulation study of sublacutrine fan sedimentation has been carried out,and the 3D models of the sublacustrine fan distribution and evolution regularity have been further obtained.The results indicate the sublacustrine fan is mainly developed in lacustrine fan system domain,which is affected by the coupling of early instability delta,strong hydrodynamic conditions and sedimentary slope break belt,and has the characteristics of multiple periods,double provenances and wide distribution rage.Numerical deposit simulation results provide useful guidance for fine reservoir description of the sublacustrine fan.