The intensive sea use refers to acentralized development mode with multipe marine engineering projects in a specific area which were uniformly planned and deployed.It is considered as a highly scientific, efficient, and ecological method that can help to achieve an optimal balance of ocean development and protection. However, it inevitably involves high consumption of marine resources, and could even result in the destruction of marine resources. Therefore, in order to minimize the influence of intensive sea use on marine resources, detailed scientific assessments are required. By analyzing the influence of intensive sea use projects on marine resources, the main assessment components and concepts were determined, and a comprehensive assessment index system was developed based on port and channel resources (including hydrodynamic changes and port resource use), coastal tourism resources (including density of use), marine biological resources (including phytoplankton, zooplankton, benthos, and fish), marine space resources (including wetlands, the coastline, and marine space), and other resources (including the use of minerals and energy). According to the investigation and assessment of marine resources in China, the evaluation index weight, evaluation standard, and evaluation grade of the influence of intensive sea use on marine resources were determined and studied. An assessment model based on the assignment method and the comprehensive index method was also established, which can be used to assess the influence of intensive sea use on marine resources. The influence of the degree of intensive sea use on marine resources can be quantitatively determined by the comprehensive evaluation index (I) before and after the completion of an intensive sea use project. Based on this model, when I < 25, the marine resources suffer a slight impact; when 25 ≤ I < 50, the marine resources suffer a general or moderate impact; when 50 ≤ I < 75, the marine resources suffer a larger impact; and when I ≥ 75, the marine resources are severely affected. By using this evaluation method, the influence of intensive sea use on marine resources in the Caofeidian area was assessed. The results showed that the influence of intensive sea use in the Caofeidian area was large, indicating that the intensive sea use project should be strictly controlled in this area.