Xiaonanhai landslide in Chongqing city is a high landslide occurred in relatively low seismic intensity regions

its causes have been puzzled. This paper is based on the related research materials of Qianjiang Xiaonanhai

through the recovery of the Xiaonanhai slope instability analysis

to calculate the seismic force’s critical conditions that make rock mass collapse sliding. Only after the topographic ampliflcation effects of seismic waves can landslide start. In order to further validate the calculated conclusions

by using UDEC software

a typical two-dimensional space model of the Xiaonanhai is established. Applying the corresponding seismic force on the slope to simulate the whole process of landslide

as to research in the mechanism that a steep slope parallel to the surface of the structure controlling the high rocky slopes triggered by topographic amplification effect under earthquake. The results show that

in the process of seismic wave propagation

the high and steep terrain with a parallel slope controlled by steep structure plane

have a significant amplified effect on seismic wave. Amplify peak acceleration-the increasing amplitude forces rock mass along the controlling structure planes which parallel with slope to crack quickly-slip along the gently dipping levels-high-speed detach from the slipping source region-huge potential and kinetic energy drive rock mass to do long-distance movement; meanwhile

accompanied by disintegration

collisions between particles and scraping effect

even with two-phase or three-phase fluid properties

which is the movement mode of this slope. Analysis reveals that the particle acceleration in the slope body has terrain amplification effects under the action of seismic force. Comparing the speed amplification factor of monitoring points between structural surface and bedrock

it is proved that the slide starts with a greater acceleration

when faces with discontinuities structural surface which parallels

to the slope

the dynamic response of slope becomes strong and eventually lead to slope’s instability.