Abstract: The Bohai Sea, the only semi-enclosed inland sea in China, is one of the most serious coastal areas with environmental problems among the offshore area. In recent years, with the increasing attention of the government to environmental protection and governance in the Bohai Sea, the deterioration of water quality has been curbed. However, due to the lack of a control mechanism for land-sea integration and departmental and regional linkage, the effective implementation of emission reduction measures is restricted. The key measure to solve this problem is to build informatization and an intelligent system that supports land-sea coordinated monitoring and evaluation. Thus, by taking Laizhou Bay as a typical application scenario, this paper implements the following major functions through the construction of land and sea pollution source multi-level monitoring and evaluation analysis system: high-precision multi-level land-sea linkage monitoring and evaluation, pollution source analysis, change of seawater quality, and sea pollution response analysis. These functions further provide a reference decision-making platform for clarifying the relationship between the water quality changes and terrestrial pollution sources, establishing a technical system for controlling the total amount of pollutants into the sea, and providing an efficient and accurate emission reduction plan.