Land use change, including urbanization, has resulted in a series of environment problems. As the world continues to be urbanized at an increasing pace, our urban ecosystems and landscapes must be made more sustainable through improved management practices. To achieve this goal the structure, function, and sustainability of urban green spaces must be better understood because they provide a series of ecosystem functions and services. Urban greenspace and its functions are under increasing pressures induced by urbanization, including land conversion into impervious surfaces, soil pollution, air pollution, and intense disturbances. Ecological assessment of urban green space cans provides valuable information for urban planning and management, in order to protect and enhance ecosystem services of urban green spaces. Urban greenspace assessment includes several aspects. First, the structural assessment of greenspace can be carried out at multiple scales. On a local scale, structural evaluation focuses mainly on species composition and vegetation structure. With the use of GIS and remote sensing data, landscape pattern analysis of urban greenspace is often conducted at the regional scale. Here, we also review research methods and advances in the study of ecological functions, ecosystem services,and sustainability of urban greenspace. Our results show that an increasing number of methods have emerged in recent decades for assessing the ecosystem function and services of urban green spaces on both local and landscape/regional scales. Some of the methods are quantitative and economically oriented (i.e. developed to valuate greenspace ecosystem services monetarily). Among numerous ecosystem functions of urban greenspace, the carbon sequestration capacity, cooling effect, and humidifying effect have received greater attention from researchers. Despite its importance for urban sustainability, ecological risk assessment of urban green spaces has been rarely studied so far. Evaluation of urban ecosystem health and sustainability is challenging, and still in its infancy, demanding more emphasis in future research. Based on the review of previous work, we propose a conceptual framework for studying and assessing urban green spaces, with a particular emphasis on humans roles in the holistic urban ecosystems. Ecological assessment of urban greenspace must be conducted periodically, with long-term monitoring systems established. Assessment and monitoring should be integrated into the management and planning of urban landscapes following an adaptive approach.