As strong earthquakes with magnitude more than 5 have occurred in Korea, the importance of seismic design has been emerging. Especially, the seismic behavior of slopes can be directly related with various damages since Korean terrain contains large mountainous area. However, there is a lack of understanding of the complex amplification characteristics of seismic waves within slopes, and particularly in Korea, seismic design criteria is not systematically established, such as the use of conventional conservative design methods. Based on these problems, this study aims to understand the complex amplification characteristics of the seismic waves within the slope and to verify the existing design method. To do so, dynamic centrifuge tests, which can reflect the soil stress condition in field, were performed. From the test results, factors affecting amplification of seismic waves are determined such as effect of soil nonlinearity and frequency contents of input motion. Moreover, it is examined that existing design criteria can result conservative outcome compared to the true behavior. Consequently, it is thought that this study will provide a clearer understanding of the dynamic behavior of slopes, and could be utilized to suggest a more reasonable seismic design criteria of slopes.