Abstract: During the reconstruction of the ship lock, excavation of the rock masses on both sides is often required. In current practice, slope instability is commonly judged using indicators such as displacement, the extent of the plastic zone, and the number of numerical iterations. These criteria typically rely on manual interpretation, which can be subjective and may not clearly determine whether slope failure has occurred. Thus, this paper proposes a slope stability analysis method based on a kinetic-energy evolution criterion, and applies it to the reconstructed ship-lock slope at Baishi Hydropower Station. A representative excavation cross-section at the ship lock is selected and the strength reduction method is adopted to analyze the kinetic energy evolution of the slope soil under different reduction coefficients, thereby identifying the occurrence of instability and failure. The proposed criterion is further compared with the conventional static assessment method based on displacement. The results show that the dynamic analysis method based on the kinetic energy evolution can obtain an accurate slope safety factor. Compared with the traditional displacement judgment method, the method proposed in this paper provides a more objective and explicit identification of slope instability which has greater advantages. The findings of this paper provide practical value and guidance for the high rock slope engineering, which can serve as useful reference for professionals in related fields.