Abstract: The Patagonia continental shelf sea, located at the southern tip of South America, is an area with significant tidal range in the world, and the dominant tidal component is M₂ tidal component. Previous studies showed that the significant tidal range in the area was caused by the resonance due to the width of the continental shelf. However, this resonance theory can’t provide a reasonable explanation for the different tidal ranges for Grande Bay, San Jorge Gulf and San Matias Gulf within the continental shelf. This article focuses on two bays, Grande Bay and San Jorge Gulf, by constructing a high-resolution finite volume community ocean model (FVCOM) and setting a series of numerical experiments to further investigate in depth the modulation of tidal amplitude by the shoreline morphology and water depth by changing the shoreline morphology and water depth. In addition to the shelf resonance, we found that the length of recessed arc-shaped coastline and the position of the headland modulate the tidal amplitude of Grande Bay and the headland and the tidal amplitude of upstream bay affects tidal amplitude of San Jorge Gulf. The local depth and bottom friction also have some influence on the tidal amplitude in San Jorge Bay.