Abstract: The hydrodynamic and water quality model of Guangzhou-Foshan Pearl River tidal river network is constructed based on EFDC,the model is calibrated and verified by the monitoring data of water quantity and water quality of 4 important control sections and 113 important primary tributaries,and the response relationship between pollution discharge of primary tributaries and water quality of control sections is established. The model quantifies the contribution rate of each tributary to the water quality control section,and takes the water quality improvement target of the important section as the constraint,obtains the allowable discharge value and reduction quantity of the main primary tributaries through the optimization solution of the model,determines the improvement target of the tributary,and provides important technical support for the diagnosis and identification of pollution problems,the improvement of hydrodynamic conditions and the promotion of water environment quality.