The rapid economic development and land utilization in coastal cities are closely intertwined with the marine ecological environment. Against the backdrop of integrated land-sea coordination planning, comprehensively understanding the evolution and spatial distribution characteristics of land-sea ecological environmental quality and exploring the coupling and coordination relationship between them holds significant practical implications for enhancing the coordinated management of land-sea ecological security. The comprehensive evaluation of ecological environment quality in both land and sea has always been a hot topic of academic research. Having a comprehensive understanding of the ecological environment quality in both land and sea is a fundamental issue in studying the overall ecological security of land and sea, and is also a prerequisite for effective planning.Taking 53 coastal cities in China as a case study, this research employs the "Vitality-Organization-Resilience (VOR)" model to assess the health of terrestrial ecosystems.The vitality of terrestrial ecosystems is reflected by Net Primary Productivity (NPP), while landscape heterogeneity, landscape shape, and landscape connectivity represent the organization of terrestrial ecosystems. Habitat quality represents the resilience of terrestrial ecosystems.The TOPSIS method is utilized to evaluate the quality of the marine ecological environment by constructing an index system. Construct an index system from the three aspects of marine water environmental quality, marine sediment environmental quality, and marine biological environmental quality to reflect the level of marine ecological environment quality.Furthermore, a coupling coordination degree model is employed to analyze the level of coupling and coordination of land-sea ecological environment quality. Relevant suggestions are proposed for cities with imbalanced development of land and sea ecological environment quality, as well as those transitioning from coordination to imbalance. The findings indicate that: 1) From 2010 to 2020, the health of terrestrial ecosystems in coastal cities exhibited a distribution pattern of "lower in the north and higher in the south," with the Hangzhou Bay serving as the primary dividing line; 2) From 2010 to 2020, the quality of the marine ecological environment in coastal cities demonstrated an improving trend, with the ranking of marine ecological environment quality as follows: East China Sea Economic Zone ＜ Bohai Sea Economic Zone ＜ Yellow Sea Economic Zone ＜ South China Sea Economic Zone; 3) From 2010 to 2020, the coupling degree of land-sea ecological environment quality in coastal cities further strengthened, with higher coordination observed in southern cities compared to northern cities. This study provides a scientific basis for the management of land-sea ecological environment and the implementation of tailored ecological restoration work in China's coastal regions, which is of paramount significance for the healthy and synergistic development of land-sea ecosystems.