Using the theory of elastic-plastic dynamic FEM and the Drucker-Prager yielding criterion, taking the time history of earthquake motion which fitted by the graphs of standard response spectrum on Ⅰ & Ⅲ types of site in the standard of Aseismic Design, as the earthquake input, to a typical loess landslide, in this paper the dynamic analysis and calculate on influence of earthquake motion to loess slope instability are made. The strain characteristics of loess slope in earthquake motion progress in different PGA, Tg and last times are analyzed. The result shows how the earthquake engineering characters influence on the stability of loess slope and displays the dynamic response of soil and change regularity of stress.