Abstract: How to consider the seismic forces within slopes is critical in seismic stability analysis. This paper reviews commonly used simplified methods for evaluating seismic inertial forces within slopes, including the pseudo-static method (PSM), pseudo-dynamic method (PDM), and modified pseudo-dynamic method (MPDM). By integrating the spiral sliding surface with the Janbu method, this study investigates the dynamic response characteristics of slopes under different calculation methods and evaluates the seismic stability of slope models with varying parameters. Finally, the seismic stability results obtained from the PSM incorporating dynamic response characteristics are compared with those from the MPDM. Results show that the MPDM_E (MPDM with elastic bedrock assumption) can avoid over-amplification of seismic inertial forces and distinguishes dynamic response characteristics at different locations of the slope, making the dynamic response a function of the model's geometry, material properties, and seismic motion parameters. The average amplification factors calculated by MPDM_E increase initially and then decrease with the increase in harmonic wave frequency, peaking at ωH₀/vₛ = π/2. By incorporating the average amplification factor into the PSM, the calculated safety factors closely match those obtained from MPDM_E. The conclusions of this paper provide a new approach for rapidly and accurately evaluating the seismic stability of slopes, further promoting the modernization of slope seismic stability analysis.