By using seismic risk analysis theory and artificial ground shaking acceleration techniques, the ground shaking acceleration history, used in Newmark method for slope stability evaluation, is created. Via a loess slope case computation, the relation between the peak acceleration in landslide and depth is deduced. In addition, a terminology, equivalent peak acceleration is put forward, and computing results by using equivalent shaking acceleration in the slope and shaking acceleration on the slope surface in Newmark method are compared.