To obtain correctly, design of the structures under seismic loads, the methods of equivalent static and dynamic analyses are usually used. The assessment of the response of entire system soil-structure under seismic load is a fundamental step to anticipate losses and help to mitigate it. Some methods of the design of retaining walls under seismic loads require the knowledge of the maximum acceleration of seismic signal. The present work discusses these methods and a comparison with detailed analysis. Three configurations of a retaining wall at different heights were considered under seismic loading: 10 signals from the 2003 Boumerdes earthquake and the 1999 Ain-Témouchent earthquake (in Algeria). Then it was assessed the dynamic thrust forces given by the approximate methods for maximum acceleration of the considered earthquakes. The approximate methods used are the pseudo-static method, the method of Seed and Whitman, the approach given in the Algerian seismic code RPA99 and the Mononobe–Okabe method. The results show that the integration of time history of seismic loading to evaluate the dynamic active earth pressure behind retaining walls is very important and can transmit higher values than the seismic force calculated by the simplified methods. This demonstrates that an earthquake cannot be considered only by its maximum acceleration and to properly design the retaining structures, the developed energy during an earthquake must be taken into account.