Considering a 2D sedimentary basin model, the D-P elastoplastic model was used to simulate the nonlinear characteristics of the basin. Combining the explicit finite element method with the viscoelastic boundary method and changing the dip angle of the basin edge, the seismic response of the basin surface was analyzed in time and frequency domains, and the difference between linear and nonlinear seismic responses of the basin was compared. The following results are presented: (1) The influence of soil nonlinearity on ground motion in the entire basin is observed. Only considering the nonlinearity, the amplification factor of ground motion is reduced by 30%-50%. Meanwhile, considering the influence of nonlinearity and dip angle, as well as the range and position of areas with the strongest amplification change, the distribution characteristics under considerably small dip angles are different. (2) The amplification factors of the two components tend to increase with the edge dip angle, but the basin edge area is most affected by the nonlinearity. In addition, under the input of a real seismic wave, the range of significant amplification area and the difference between linear and nonlinear results are relatively large. (3) Considering the nonlinearity, the amplification factors of seismic waves with various frequencies are different. However, the distribution of the spectral ratio from low to high frequency is increasingly complex, and the influence of the basin dip angle becomes evident with the increase in frequency. (4) Considering the nonlinearity of soil, the overall characteristics of seismic wave propagation are maintained, but the strength of each seismic phase is reduced.