The rivers connecting oceans generally carry sediment due to water and soil losses in China. Additionally, the maximum sediment concentration is 300 g/L, which is much higher than that of other countries. It is unknown whether seawater with sand particles will affect the power of tidal current turbine blades. It is therefore necessary to study the capture power of tidal current turbines in the water-sediment environment. In this study, the blade was divided into a number of transversal airfoil elements based on the blade element theory. The CFD-DPM model was employed to study the lift and drag coefficients of airfoil under multiphase flow, and the fluid–particle interaction was considered. The accuracy of this presented model was assessed using the experimental data of a 120 kW tidal current turbine in a water-sediment environment. Good agreement between the predictions and experimental data was observed. The effect of particle properties on the lift coefficient and the drag coefficient of airfoil were investigated in detail. Furthermore, the 120 kW tidal current turbine power was calculated based on the Blade Element Momentum theory under different particle concentrations. The results show that small diameter particles can improve the tidal current turbine power and the large diameter particle can reduce the power.