Abstract: Wetland is an important part of the ecosystem, and the investigation of wetland pollutant migration under the combined effect of submerged vegetation and bed absorption boundary can provide a reference for wetland design and maintenance.The random displacement model based on the Lagrangian method is adopted to simulate the transport process of instantaneously released pollutants in wetlands with dense rigid submerged vegetation and bed absorption boundary by setting different vegetation densities and bed absorption probabilities for the pollutants.Results indicate that the increase of the bed absorption probability accelerates the average migration velocity of the pollutant particle cloud and weakens its longitudinal dispersion, while the increase of vegetation density inhibits the bed absorption, extending the stay and greatly dispersing the distribution of the pollutants in the wetland, thereby giving full play to the comprehensive purification function of the wetland.When the absorption probability exceeds 10%, the absorption boundary of the bed can be regarded as a completely absorptive boundary.Conseqently, the use of a substrate with high absorption probability in wetland design is unnecessary.