Abstract: In the base rock of the Gezhouba Dam between sandstones, and siltstones there are A number of weak intercalations consisting of claystones, silty-claystones, and their argillitgation intercalation with different thickness and behavior. Base on the results of the Quantitatire analyses of the mineral compositions and some data of grani size analysis on some representative interactions, the relation between the composition of weak intercalation, especially hydrophilic clay mineral composition, and the formation of argilligation intercalations is described and researched.