Abstract: The slope stability analysis is a focal problem in the geotechnical engineering field. However, few dynamic stability analyses are made based on the ever-changing modal parameters. Therefore, the cohesion in key regions is taken as the dynamic parameter so as to realize the dynamic stability analysis of the slope. By using GIS (geographic information systems) 3D slope stability analysis models, the cohesion can be adjusted by real-time data of natural vibration frequencies in order to make the strength reduction method more real and effective. The establishment of the inherent relationship between the vibration frequency and the cohesion of landslide can effectively solve the difficulty of selection and adjustment of the parameter in numerical analysis. The experimental results show that the dynamic stability analysis based on the variation of modal parameters makes full use of the objective advantages of strength reduction and avoids the subjective disadvantages of the limit equilibrium method. Thus, the simulated results are more close to the actual conditions. Furthermore, this new method can take into full account the slope space features and allow an objective evaluation of the strength retrogression, so it is reliable for slope stability analysis.