Abstract: The application of high resolution sequence stratigraphy on stratigraphic classification and comparison comes more widely and shows more advantageous. Sequence stratigraphy breaks traditional view of cycle stratigraphic classification and comparison and makes full use of isochronous comparison. But sequence classification of alluvial - fluvial facies is the difficulty in research on the sequence stratigraphy, which is due to hard identification of base level cycle. This article draws the conclusion of the character of base level cycle in the lower member of ES4 in Weicheng oilfiled through the rock core analysis and extends its application to multi wells profile, which formed base level cycle isochronous comparison frame work profile. Stratigraphy of the lower member of ES4 is divided into 2 medium term cycles and 10 short term cycles.