Vegetation plays a significant role in river ecosystem, which has a great influence on hydraulic structures and sediment transport. Understanding the vertical distribution of suspended sediment concentration (SSC) in canopy flow is helpful to study the process of riverbed erosion and deposition in vegetated channels. Aiming at the sediment-laden flow in open channel covered with submerged vegetation, this study divides the water depth into two layers along the vertical direction with the vegetation height as the boundary and then proposes a new SSC distribution model based on gravitational theory to estimate the vertical distribution of relative SSC in the free water layer and vegetation layer respectively. In the meanwhile, a new formula is also proposed to evaluate the Reynolds shear stress below the submerged vegetation height, which has been successfully applied in the derivation of the new SSC distribution model. The validation results of the simplified velocity model, the new Reynolds shear stress formula and the new SSC model compare well with the collected experimental data series. On top of that, it is found that the uniformity of SSC distribution profile progressively decreases with the increasing sediment particles diameters. Besides, according to the validation results and discussion, it is believed that the controversy point about gravitational theory would not have obvious influence on the estimation of SSC distribution so that the gravitational theory can be adopted to investigate suspended sediment transport in vegetation flow. That would be benefit for river ecological restoration and better management.