The blue-green space in Chinese cities is important for urban land use. Exploring the spatiotemporal dynamics and driving factors of blue-green spaces under rapid urbanization processes contributes to unveiling the evolutionary patterns of urban blue-green spaces, which provides a fundamental basis for related research and policy formulation. In this study, remote sensing imagery was used to calculate the extent of blue-green spaces from 2000 to 2020, and we analyzed the evolution using the intensity of area change, a land transfer matrix, the multi-order adjacency index, and a boosted regression tree model. This study revealed the spatiotemporal dynamics and driving factors of blue-green spaces in the central area of Hefei from 2000 to 2020, particularly: (1) Between 2000 and 2020, there was a 14.8% net increase in the total area of blue-green spaces in Hefei’s central area. (2) Blue-green spaces primarily showed fringe-type expansion and proximity-type expansion. Spatially, new blue-green patches tended to cluster around large pre-existing natural blue-green patches. Furthermore, the expansion of blue-green spaces shifted from the urban periphery to the urban interior. (3) Natural factors exerted a greater influence (80.8%) on the expansion of blue-green spaces than did socioeconomic factors (19.2%). DEM (32.1%), slope (26.9%), aspect (21.8%), population density (PD) (13%), and value-added by the tertiary industry (VATI) (6.2%) were identified as the primary driving factors. The results contribute to understanding changes in urban blue-green spaces and the driving factors behind these changes, thereby providing support for future planning, protection, and sustainable development of urban blue-green spaces.