Abstract: A 1-D and 2-D zonal coupling solution method for flow and sediment transport in estuaries is proposed.By defining f ictit ious domain at the interface of different computational sub-domains and making use of the characterist ics of non-structured meshes and element assembly procedure of the finite element method, a strong zonal coupling algorithm is established which puts all the influence coefficients of the 1-D and 2-D linking nodes into the fictitious nodal elements in the global matrix of the system equations.Compared with conventional zonal coupling algorithms which usually use simple matching conditions, the developed method can greatly improve the calculat ing stability.Finally, the algorithm is applied to simulate flow and sediment transport in an estuary.The results agree well with the measured data, and large time step can be achieved, which shows that the proposed algorithm is correct and reliable.