To study the effect of mountain topography on seismic amplification and meet the seismic design needs of mountain building in practical engineering, taking unimodal protruding topography as an example, dynamic substructure method was introduced to calculate the seismic response of 60 different-size rock bump terrains with slope angle of 30 ~ 60°, bump height of 20 ~ 80 m, and platform width 50 ~ 600 m under the ground motion input, and the seismic response law of amplification of different-size rock bump terrains was obtained. Results show that the dynamic substructure method can greatly improve the computation efficiency while ensuring the computation accuracy. The convex topography has a great influence on the amplification effect of ground motion. The response of ground motion increases constantly from base of slope to slope top, and the amplification effect of the central point of the platform is the largest. With the increase of slope angle and height, the amplification effect of topography on ground motion increases. When the slope angle and slope height remain unchanged and the topographic relief height is relatively small, as the topographic width increases, the seismic amplification effect increases; otherwise, when the bump height is larger, the seismic amplification effect decreases. The increase of topographic relief size leads to the intensification of high frequency response and the decrease of low frequency response peak.