The effect of waste landfill on seismic response of transmission tower pile foundation at mountainous slope still remains unclear. Typical models about pile foundation of transmission foundation in southwestern China mountain areas are built and analyzed using FLAC3D. Then seismic response on pile caused by waste landfill is preliminary studied under the condition where there is waste landfill around the pile or not. The results show that: compared with pile without spoil, horizontal peak acceleration, pile displacement, internal force of pile, displacement of soil around piles all increase obviously after waste landfill is built. When gradient of steep slope is larger than 35°, waste soil landfills will increase the seismic response of pile foundation, thereby seismic behavior of steep slope is reduced.