As the dynamics of tidal river network is complex with runoff and tide confluence, breach discharge in tidal river network is too complex to be estimated by empirical formula accurately. In view of this, a hydrodynamic model coupling 1-D model of river network and 2-D model of reserve area is developed with the breach as the lateral linkage. The model integrates the tidal river network and the reserve area, hence avoiding the deviation of breach discharge caused by the uncertainty of environmental factors and empirical parameters. Simulation results of typical example and embankment-break flood scene show that 1) the jet-flow of breach disperses into the reserve area, and the flow pattern is affected by the underlying surface significantly; 2) water level and discharge of the breach change with tide fluctuation, and the calculated total water amount according to breach discharge agrees with that from flooded areadepth. The simulation results reflect the combined influence of underlying surface, water head, tide level and flow pattern on breach flood. The proposed model is rational and reliable in calculating breach discharge and simulating embankment-break flood.