The coordinated supply and demand of ecosystem services (ESs) is important for ensuring regional sustainable development. However, research identifying key areas of imbalanced supply and demand of ESs at the urban agglomeration scale is limited. Therefore, in this study, using the Fujian Delta urban agglomeration of China as the research area, based on multi-source data, and analysis tools, such as ArcGIS, ENVI, and GeoDa, we constructed a research framework and indicator system for ESs supply and demand to determine the spatial change law, matching degree, and coupling coordination degree (CCD) of the ESs. On this basis, the key areas of imbalanced supply and demand of ESs were identified, and optimization strategies were proposed. The results showed that (1) there is obvious spatial heterogeneity between ESs supply and demand in the study area, and different degrees of spatial changes occurred with urbanization. Specifically, areas with large changes were concentrated in urban core areas and economic development zones. (2) The matching degree between ESs supply and demand is quite diverse and shows a trend of polarization. Under the influence of urbanization, some cities began facing ESs supply shortages. (3) Overall, the CCD between ESs supply and demand in the study area is in a state of mild incoordination, but with increasing urbanization, some cities have turned into a state of extreme incoordination. Our results indicate that the ESs supply and demand status in some cities at the urban agglomeration scale has become increasingly severe. Therefore, it is necessary to focus on certain "key areas" to formulate optimization strategies. For key areas with "low supply-high demand" and extreme incoordination, the population and land use intensity should be controlled to reduce the ESs demand level. Meanwhile, for key areas with "high supply-low demand" and extreme incoordination, the utilization efficiency of ecological resources should be improved to enhance the ESs supply capacity. The results of this study will help decision-makers optimize the relationship between ESs supply and demand in order to achieve the sustainable development of urban agglomeration. (c) 2021 Elsevier B.V. All rights reserved.