In order to study the characteristic of seismic response of the reinforced slope subjected to earthquake, the seismic response spectrum of slope reinforced with piles under the two different diameters were compared and analyzed. The seismic acceleration response shows a steady amplification with the increase of height without water in substratum, and the maximal seismic response occurs near the crest of slope. The dominant frequency of the amplification of seismic response spectrum of the slope reinforced with piles under the smaller diameter obviously shifts to the medium and low frequency. In addition, because of the liquefaction of substratum and the resulting dynamic failure of the pile, the response components of the medium and low frequency also are strengthened further. The results show that the global stiffness of the reinforced slope is obviously affected by the diameter of the pile and the liquefaction in substratum, which thereby affects the seismic acceleration response and the distribution of spectral amplification factor.