At present, the Newmark Sliding Block Method is adopted as a seismic evaluation method of embankments in Japan. The threshold acceleration during shaking is supposed to be a constant in the Newmark Sliding Block Method. However, threshold acceleration can be varied during strong earthquake motions. In this study, several dynamic centrifuge model tests were carried out to investigate the threshold acceleration of embankments during the shaking. The compensation in the Newmark Sliding Block Method was proposed considering variations in threshold acceleration. The test data indicate that the threshold acceleration of the embankments has a tendency to decrease during an earthquake.