The maritime defence settlements of the Ming Dynasty are a key component of China’s military cultural heritage. This study examines the three coastal defence sectors of Fujian by establishing a three-tier evaluation framework utilising GIS spatial analysis and the Analytic Hierarchy Process (AHP) for quantitative assessment. The findings reveal that the synergy between military outposts significantly enhances overall defence effectiveness, while the independent defence capability of each stronghold is crucial for withstanding external threats. A comprehensive evaluation further indicates that the Fujian central coastal defence sector, characterized by its robust economy and densely distributed fortifications, demonstrates the highest level of defensive performance. By systematically quantifying the defensive performance of Fujian’s maritime defence settlements, this study develops an evaluation model that provides a scientific basis and decision support for value assessment, sustainable conservation, and adaptive reuse of this category of military cultural heritage.