Abstract: To investigate the suspension and diffusion mechanisms of sediment particles under the action of fluids from both particle and flow field scales, a Gaussian curvature model is introduced in the discrete element method to characterize the nonlinear contact properties of non-spherical particles. Additionally, improvements are made to the drag force model and porosity models for non-spherical particles. By doing so, the polydispersed non-spherical particle CFD-DEM coupling numerical method is established. The accuracy and superiority of this model are validated through comparisons with physical experimental results. Subsequently, the suspension and diffusion processes of sediment under fluids are simulated. Results show that the sediment settling rate is positively correlated with the initial discharge quantity of particles and negatively correlated with flow velocity, while the escape rate shows an opposite trend. At high initial discharge, particle clustering effects promote fluid kinetic energy dissipation, causing gravity to surpass inertial forces and leading to rapid particle settling. At low initial discharge, higher fluid kinetic energy enhances horizontal particle transport. At lower flow velocities, particle shape significantly affects the spatial distribution of sediment particles.