Abstract: The mechanism of earthquake-induced bedding rock landslides is different from that of slope instability in a normal gravity environment, and its failure characteristics are mainly manifested as structural plane deterioration under a seismic load directly affecting the stability of the slope. Several advanced methods have been proposed to study the stability of earthquake-induced bedding rock landslides; however, the quantitative evaluation of the vibration degradation effects of structural planes and their application in the dynamic stability analysis of bedding rock slopes is a topic that requires further detailed study. In this study, the deformation and instability modes of bedding rock landslides are first analysed, and then a seismic dynamic model is proposed, along with critical instability conditions. Furthermore, a method for calculating the seismic-induced permanent displacement of the bedding rock slope, considering the effect of the deterioration of the structural plane, is proposed. Using the Huashengdi bedding rock slope as a case study, the deformation displacement results calculated using the proposed method, which incorporates the effect of the dynamic deterioration of the structural plane, were compared with results obtained using a numerical simulation method to verify the feasibility and engineering practicality of the proposed method. The proposed method was also compared with various other methods to calculate the sliding displacement of a landslide under a seismic load, and it produced more reasonable results than the other methods.