Abstract: The deposit slope is very typical along the highway from Dujiangyan to Wenchuan, China, where “5.12” Wenchuan Earthquake took place. The investigation of “5.12” Wenchuan Earthquake shows that most of the landslides occur in those slopes. In order to study the seismic failure mode of this kind of widely distributed slope, 1g shaking table model tests are carried out to study the mechanism of slope instability. According to the test results, difference responses between the deposit and the rock bed under dynamic conditions make the failure mode of the deposit slope different from those under the static conditions. A throwing phenomenon occurs at the upper part under the combination of horizontal and vertical shaking, which is widely reported in “5.12” Wenchuan Earthquake. A mathematical model is established to analyze the throwing phenomenon under earthquakes, and it is found that this phenomenon can happen only when the crack opening angle meets some conditions.