The slope stability analysis is of importance for the practical engineering, and has received widely attention. Generally, the calculation process of the traditional methods is complex. In this paper, a new method was presented to analyze stability of the simple homogeneous slope, in which the safety factor and the max slip displacement of the slope under seismic excitation can be derived based on the principle of the minimal potential energy. The proposed method was efficient and did not require any iterative process for calculation. In order to evaluate its performance, a numerical example was studied to analyze the slope stability. The numerical results show the proposed method is valid and feasible by comparing with the numerical method.