ABSTRACT: A mathematical model to predict both velocity and concentration distributions for sediment-laden open channel flow is developed. Velocity profiles are derived by theoretical analysis and numerical method. Logarithmic law and semi-empirical wake function concept are not adopted. An empirical equation for the ratio of sediment exchange and fluid diffusion coefficients is considered to solve the diffusion equation for suspended-sediment concentration profiles. Four sets of experimental data from previous researchers are compared to numerical calculation. In the engineering applications, velocity and concentration profiles of sediment-laden flow can be predicted simultaneously by the present model with the measured velocity and sediment-concentration at reference level.