Abstract: On the foundation of clearing up Kuishan formation’s stratigraphic division, this paper makes observational study on the stratigraphic features in outcrop area and coverage area. Kuishan formation lithology is dominated by quartz sandstone with variegated shale and siltstone of varying thicknesses. There are four common rock types: multi?layered sand?shale interbed type, thick sand with thick mud type,upper thick sand?lower thick shale?bottom sand type, and single thick sand type. Kuishan formation in Shandong province was single thick sand type, whose definition is too narrow. This paper suggests that Kuishan formation should be redefined as stratigraphic unit which is dominated by thick hard dense (feldspar) quartz sandstone, with shale and siltstone of varying thicknesses, and the top takes thick hard dense (feldspar) quartz sandstone as boundary with Xiaofu River formation, the bottom boundary is taken by A0 bauxite layer or horizons corresponding to it. Such a definition of Kuishan formation is the same with the top and bottom boundaries of the production field, and helpful to maintaining continuity and succession of stratigraphic division data available and avoids a lot of rework in stratigraphic subdivision and correlation