We have constrained a small-scale, dome-shaped low-velocity structure near the core-mantle boundary (CMB) of Earth beneath Perm (the Perm anomaly) using travel-time analysis and three-dimensional (3-D) forward waveform modeling of seismic data sampling of the mantle. The best-fitting dome-shaped model centers at 60.0°E, 50.5°N, and has a height of 400 km and a radius that increases from200 km at the top to 450 km at the CMB. Its velocity reduction varies from 0％ at the top to -3.0％ at 240km above the CMB to -3.5％ at the CMB. A surrounding 240-km-thick high-velocity D structure has also been detected. The Perm anomaly may represent a stable small-scale chemical pile in the lowermost mantle, although the hypothesis of a developing mantle plume cannot be ruled out.