Abstract: The soft rock widely distributed in the engineering slope can be classified into four kinds: argillized seams,coal,carbonaceous shale, and pelitic siltstone.Its origination,spatial distribution and orientation,as well as slaking characteristics directly affect the stability of the slope and design of anchoring and other supports.A careful study of the slaking characteristics of several kinds of soft rock formations in soft zones such as faults F3,L9,L10,Lc,L11 etc.,uncover that the soft rock highly absorbs water,which facilitates argillization,softening,and slaking.A circulated slaking experiment shows that the degree of slaking is highly related to the ratio of clay in the soft rock and times of the slaking.According to the degree of the slaking and shape of the slaking substance,the slaking process can be divided into five types of slaking rock and 5 kinds of failure patterns.The paper further discusses the slaking mechanisms.