Abstract: The excavated slope with multi-layer weak interlayer has the characteristics of complex slope structure and difficult stability evaluation and treatment. Based on the on-site excavation of high slope in western Guizhou, an indoor physical test model is carried out. Through excavation under different working conditions, the evolution process of deformation and failure is presented. The deformation and failure model and formation mechanism are analyzed to determine the instability and failure range. The results show that the fissures in the excavated slope extend from the surface to the inside, from top to bottom, from the initial steep short fissures, and finally through to form a long fissure approximately parallel to the rock layer; the deformation and failure of gentle slope excavation is shallow surface, the overall stability is good, and the instability range and scale are small; the excavation deformation and failure scale of steep slope is large, and the stability is poor, mainly in the deep instability of slip tensile fissure; the slip surface of shallow landslide is mainly sheared by interlayer argillaceous interlayer, which is basically linear; the sliding surface of deep landslide is stepped by the combination of interlayer argillaceous interlayer shear and steep inclined fractures. The research results have important guiding significance for the design, stability evaluation and treatment measures of bedding excavation high slope in western Guizhou.