This study is aimed to investigate, as a solitary wave propagating past a cavity; the motion of fluid particles inside a bottom cavity. A model formulated with stream function and vorticity is applied and the governing equations are solved using the finite-analytic method. In order to reveal the small eddy motion in a cavity, a boundary-fitted grid system combined with fine overset grids is adopted. The simulated motions of fluid particles at various times are shown to be similar to the experimental observations. The present model is demonstrated to be capable of capturing the motion of the fluid particles. Furthermore, the effect of incident wave height on the patterns of fluid-particle motion and the removal displacement along the vertical and horizontal directions are analyzed and the results are presented and discussed.