Urban green infrastructure (UGI), serving as the essentially ecological barrier of cities, is an important way to solve urban environmental problems. It is of great significance to study the spatiotemporal pattern and morphological evolution of UGI in rapidly urbanizing area for optimizing the network and layout of urban green space, improving the urban living environment and enhancing the city's sustainable development capacity. Using the Google Earth Engine (GEE) platform, the vegetation index and water index of about 4,800 Landsat images from 2000 to 2019 were calculated, then the UGI of central Liaoning urban agglomeration was extracted by using the index threshold method in this study. On this basis, using the landscape metrics and the morphological spatial pattern analysis (MSPA), a continuous time series analysis was further conducted to explore the evolution trends of the UGI landscape pattern in central Liaoning urban agglomeration from 2000 to 2019. The results indicated that the UGI area of central Liaoning urban agglomeration showed an upward trend, increasing by 62%, from 170.28 km² in 2000 to 275.68 km² in 2019. Due to continuous urban expansion, its proportion of urban built-up area declined gradually from 25.73% in 2000 to 19.72% in 2019, indicating that urban green space construction lagged behind urban expansion. During the study period, fragmentation of the UGI in this urban agglomeration intensified, the dominant patches' area decreased, the patches' shape tended to be unconscionable and diverse, the UGI landscape became spatially dispersed and patches cohesion of UGI decreased. In addition, the UGI was gradually encroached on and transferred to other types of UGI, such as edge, bridge areas, branches and loop, or non-UGI landscape with the urban area expansion, its proportion in UGI decreasing from 46.2% in 2000 to 37.26% in 2019; the UGI in urban's margin changed more intensively and was more affected by the urbanization process. This research can provide technical and decision-making supports for the layout and optimization of UGI network in rapidly urbanizing areas and the construction of UGI-based urban ecological security pattern.