Abstract: The flux monitoring method of periodically monitoring the flow rate and water quality of each drainage outlet is the most effective way to calculate the amount of land-based pollution entering the sea. However, most cities in China have not established a complete monitoring system, resulting in a lack of basic monitoring data and difficulty in accurately calculating the amount of pollution entering the sea, which affected the formulation of the total control plan for pollutant discharge into the sea under the coordination of land and sea. Based on the research work carried out by Shenzhen in the construction of the National Marine Comprehensive Management Demonstration Zone and the pilot project for controlling the total amount of pollutants discharged into the sea, especially in response to the complex impact of large-scale river interception systems on natural drainage patterns, Successfully explored the application of total pollution calculation method in the calculation of land-based sea pollution from the perspective of urban water supply and drainage system, effectively addressing the problem of lack of periodic monitoring data, and can be promoted in other bay areas. Taking Shenzhen Bay in Shenzhen as an example, COD, NH₄-N, and TP were selected as typical pollutants.