The dynamic interaction mechanism of soil and large-diameter belled piles is an important factor in earthquake engineering research. Based on the Lagrangian FLAC^3D program, we established three-dimensional numerical models of the dynamic belled pile-soil interaction and dynamic equal-diameter pile-soil interaction under seismic loading to investigate the difference in the seismic responses of the large-diameter belled pile and conventional equal-diameter pile. We used the Mohr-Coulomb elastic model to consider the nonlinear characteristics of the soil around the pile and the linear elastic model to simulate the pile itself. We then used the model cutting method to set the interface between the pile and its surrounding soil. Under the input of a 5·12 Wenchuan seismic wave, we performed a numerical calculation and analysis of the seismic responses of the two pile foundations. The results show that the anti-seismic performance of the large-diameter belled pile is better than that of the conventional equal-diameter pile. A comparison of the acceleration time history curves with a dramatic difference shows that the belled pile is not sensitive to the dynamic displacement response.