Abstract: How to consider the seismic forces within slopes is critical in seismic stability analysis. Studying the dynamic response mechanism of slopes during earthquakes helps evaluate their stability. Firstly, this paper discussed commonly used simplified methods for assessing seismic inertial forces within slopes, including the pseudo-static method (PSM), pseudo-dynamic method (PDM), and modified pseudo-dynamic method (MPDM). Secondly, by integrating the spiral sliding surface with the commonly used Janbu method in slope stability analysis, this study investigated the dynamic response characteristics of slopes under different calculation methods and evaluated the seismic stability of slope models with varying parameters, covering a total of 19, 683 scenarios. Finally, the seismic stability results obtained from the pseudo-static method incorporating dynamic response characteristics are compared with those from the modified pseudo-dynamic method. Results show: The MPDME, using an elastic bedrock assumption, prevents over-amplification of seismic inertial forces and distinguishes dynamic response characteristics at different locations of the slope. The resulting dynamic response is a function of the model’s geometry, material properties, and seismic motion parameters. The average amplification factors calculated by MPDMS and MPDME increase initially and then decrease with the increase in harmonic wave frequency, peaking at ωH₀ / vₛ = π/2. If the average amplification factor is incorporated into the PSM, the calculated safety factors closely match those obtained from MPDME. The results in his study can facilitate rapid and accurate evaluation of slope seismic stability and promote the modernization of seismic stability analysis of slipe in China.