<p>Coastal cities play a pivotal role in China’s strategic approach to fostering external connectivity through coastal regional development. This study constructed an evaluation system by employing a Pressure-State-Response (P-S-R) framework and evaluated the ecological efficiency of the 13 coastal cities in China from 2017 to 2021. The super-efficiency Slacks-Based Measure (SBM) model has been applied to evaluate the comprehensive eco-efficiency at the city level from the dimensions of resource input, economic development, and environmental pollution. The Geographically and Temporally Weighted Regression (GTWR) was implemented to examine the spatial and temporal impacts of urban green space and additional influential factors on ecological efficiency. The findings indicate notable variations in ecological efficiency across diverse cities. The comprehensive evaluation scores of coastal cities in the Bohai Sea region exhibited a general upward trend across resource input, economic development, and environmental pollution, resulting in an increase in ecological efficiency over the years. In terms of economic development and resource input, the evaluation scores of cities showed a similar trend, with economic development scores generally higher than resource input scores. However, cities with higher economic development scores generally faced more serious environmental pollution issues. Green space was the main driving force of ecoefficiency in coastal cities, which ranged from − 2.487 to 7.831, indicating different levels of impact on ecological efficiency. The main reasons may be because green space can regulate the water cycle, reduce waste and loss of water resources, maintain the balance of the hydrological cycle, filter and purify runoff water, etc. This study offers a theoretical framework and policy suggestions for the future planning and ecoefficiency development of coastal cities.</p>