It is necessary to accurately estimate the settlement caused by earthquakes so that more stable retaining structures can be designed and constructed. The authors had carried out dynamic loading model tests by employing a centrifuge apparatus. Based on a series of small scale model tests subjected to dynamic forces a method for predicting the deformation of retaining walls is proposed. The effect of the strength, length and the number of reinforcement on the strength and deformation of the wall is evaluated. It is found that the stiffness of the reinforced wall can be expressed well in terms of these three parameters.