Ships sailing in shallow water areas with uneven seabed often suffer from shallow water effects due to channel limitations. At the same time, due to the uneven seabed, the hydrodynamic performance will undergo more drastic changes, which will have a negative impact on the safety and maneuverability of the ship. Therefore, based on STAR-CCM+, analyze and calculate the influence of step bank and shallow water depth on the hydrodynamic performance and flow field of ships. The results indicate that the hull undergoes obvious heave and longitudinal tilting motions after experiencing step bank, and the stern roll of the hull occurs when the hull is sailing on the step bank, and then gradually changes from stern tilt to bow tilt. The hull resistance reaches its maximum when the stern reaches the step bank, in which the change in total drag is mainly due to the residual drag.  During the shallow water area, the bow wave gradually decreases, and the transverse wave and scattered wave in the stern wave area have a tendency to merge.