In order to explore the effects of bioturbation on material exchange in coastal wetlands, a controlled laboratory experiment that made crabs as research object was conducted to study the effects of different crab densities on sediment geomorphology changes and water and salt transport under simulated tidal conditions. The results showed that crabs carried a large number of deep sediments to the surface, forming a rugged microtopography, which resulted in a significant increase of sediment surface area. Crab activities not only effectively promoted the exchange of surface water and groundwater but also accelerated salt migration process of shallow soil. The amount of surface water and groundwater exchange and salt transport increased significantly with the density of crabs. Therefore, it could be concluded that bioturbation is an important factor affecting sediment geomorphology, which greatly accelerates water and salt exchange in coastal wetlands.