Abstract: The disaster-causing range formed by the earthquake landslide is an important basis for judging whether the landslide can cause losses to existing structures and determining the early warning evacuation range. Therefore,it is necessary to study the sliding body size and disaster-causing range after the post sliding of soil slopes triggered by the earthquake. Based on the dynamic SPH analysis method,combined with the elastoplastic constitutive model and the governing equation of solid mechanics,we establish a dynamic analysis model for the seismic soil slope failure. By setting the vibration boundary particles and the free field boundary particles,we realize the application of ground motion acceleration and the simulation of the free field boundary. We use the dynamic SPH analysis method to simulate an existing shaking table test for soil slope. And we obtain a sliding form similar to the shaking table test slope from the SPH simulation. This result verifies the accuracy and precision of the dynamic SPH analysis method. Afterwards,we design calculation cases of soil slopes with different slope angles. And we carriy out SPH analysis considering the influence of ground motion acceleration amplitude. Finally we obtain the sliding body size and the disaster-causing range of landslide after instability of seismic soil slopes under various working conditions. The simulation results show that the soil slope has a similar sliding surface under the action of different ground motion amplitudes. And the potential sliding area increases with the increase of the ground motion amplitude. Meanwhile,the stability of the soil slope under different ground motion acceleration amplitudes shows a downward trend. And the disaster-causing range becomes larger,while the sliding body size is decreasing.