In general, a certain value of acceleration is applied to the sliding mass when analyzing the seismic stability of landslides，which ignores the propagation of seismic wave during the process. However, the failure of a landslide in an earthquake is fundamentally caused by the occurrence of the acceleration difference between the sliding body and the sliding bed when seismic waves propagate in rock and soil. In this study, a formula was deduced to calculate the acceleration difference. Taken the Yushu airport road landslide III in Qinghai province as an example, the dynamic input was referred to the time history curve of acceleration recorded at the airport seismological observatory in Yushu earthquake. Meanwhile, the time history curve of the dynamic stability coefficient of the landslide was obtained by using the transfer coefficient method. The calculated results show that the stability coefficient of the landslide in natural state is 1.269, the minimum dynamic stability coefficient is 0.962, and the minimum average stability coefficient is 1.069. The above results indicate that the overall stability of landslide is good. Although the entire failure of landslide would not occur in an earthquake, some local deformation happens. It is also verified that the calculated results are consistent with the observed phenomenon after the earthquake.