In order to investigate the stability of piles under dynamic loads, an indoor model test was designed, in which homogeneous fine sand was used to simulate the subsoil around the pile shaft with various diameters, embedded ratios and boundary conditions at the top and the toe. Then, simple harmonic loads with different vibration amplitudes and frequencies were exerted at the pile top, and the corresponding dynamic responses of the pile shaft and subsoil (including dynamic stress and strain, etc) were measured with the sensors instrumented among the pile-soil system. Based on the test data obtained, a comparative analysis was made to discuss the dynamic influencing rules of various parameters (such as the diameter and embedded ratio of pile shaft, the frequency and magnitude of dynamic load, etc) on the pile top displacement. Furthermore, the parametric resonance phenomenon of the pile was observed and verified in the test. And the difference between the smaller frequencies measured and the theoretical values may be improved by a coefficient of k ranging from 0.5 to 0.8, which decreases with the increase of the dynamic load amplitude and the depth of subsoil.