Based on the analysis of the characteristics of river evolution and water and sediment in the proposed river section in recent years,and taking into account the law of water and sediment movement in the Nanjing reach of the lower Yangtze River,the variation of sediment volume after the impoundment of the Three Gorges Reservoir and the hydrological years that have adverse effects on the erosion and siltation of the river bed,representative models are established to calculate the water and sediment control conditions and unfavorable water and sediment.Combining with the measured data,a two-dimensional tidal current and sediment mathematical model is used to simulate and verify the tidal current and sediment concentration in the vicinity of the proposed Ningxi Road river-crossing tunnel in Nanjing Reach of the Lower Yangtze River.On the basis of the good verification,the river bed erosion and deposition for engineering of each scheme(A,B,D,E）is forecasted and compared with physical model test results.The results show that the calculated results of the two models are quite consistent；the scouring changes of the proposed cross-river tunnel schemes are basically similar,and the scouring depth of the left and right deep grooves of the E scheme is the smallest,which can provide a scientific basis for the reasonable implementation of the cross-river tunnel project.