In this paper, one-dimensional, unsteady and cross-sectionally averaged Saint-Venant-type model was used for flow modeling in tidal river network of Pearl River Delta, China. A three-staged approach is employed for the solution of river network hydrodynamic equations. To model the influence of an accident release of high cadmium concentration in upstream of Pearl River Delta, a cadmium model in considering the exchange between water and sediments was coupled with the hydrodynamic model. The river network was divided into 582 calculated river reaches with length ranging from 500 m to 2500 m. With a time step of 10 min, the hydrodynamic model and cadmium model were respectively calibrated and verified. Modeled stage/discharge and cadmium concentration were found matching well with the measured data. The roughness of river reaches in Pearl River Delta was calibrated to be 0.016 to 0.044. Several scenarios of accident release of pollutants with high cadmium content were modeled. Distribution of cadmium concentration at selected sections under accident release in river network of Pearl River Delta were given. The modeled results put forward a base to deal with pollution accident in Pearl River Delta where important water source sites are located.