Abstract：In sequence-stratigraphic analysis ,the identification of stratigraphy-sequential interfaces and definition of the nature of interfaces are more important. In continental basin, the sequential interface are usually formed in transitional position between rising and falling of datum, that is the position of minimum ratio between capable space and sedimentary supply. In that period，the source supply was abundant，sand body was development and the causes of forming sand body and distribution of sand body are changed around the interfaces，so that the accumulation conditions and types of different sandy bodies are very different. Faced with more than tens meters of sand rock developed in Paleogene S3 Zmiddle Segment in Fandong area，Dongying depression,the sequential interface is determined by using the ratio between capable space and sedimentary supply, it's considered that delta front slum turbidite sand bodies are developed under the interface，above the interface，the basinfloor fan sand bodies caused by turbidite current and slope fan sand bodies caused by gravity flowtraction current are developed.
