In this article, dynamics numerical simulations are conducted to investigate the amplification of peak ground acceleration of high-steep rock slope. The relations of amplification factors in the crest and surface of slope with the height and gradient of slope are studied in the presence of harmonic wave and El Centro seismic wave. According to the computation results, the isolines of horizontal and vertical amplification factor of cross-sectional slope are plotted to analyze the amplification factor distribution in slope. Results indicate that amplification factor does not continuously increase with the rise of slope height. The maximum amplification factor appears in the crest of slope, and fluctuates in a range of no more than 2.0. Amplification factor in the top surface of slope gradually decreases as the distance from slope crest increases. The spatial distribution characteristics are markedly different between horizontal and vertical amplification factors in the slope. In the area near the crest of slope, vertical amplification factor is up to 1.5. The influence of vertical amplification factor cannot be ignored in the seismic design of high and steep slope.