Abstract: The research achievements about weak intercalated layers of bedding rocks are presented in this paper, which were made by the author and his colleagues in the past 30 years. A lot of work made are related to the stability analyses for slops of large-scale open-pit minings, and for bed rocks of key water conservancy projects. The emphasis of this paper is put on shearing testing method in-situ, and the research results of deformation and strength properties of weak intercalated layers.