As an ecological strategy of nature-based solution, green roofs can effectively alleviate a series of ecological environmental problems in urban cities. In order to better tap the application potential of green roofs in urban ecosystem, it is necessary to comprehensively and quantitatively understand the correlation mechanism between green roof and urban ecosystem starting from the regulation services of green roofs. Therefore, this paper firstly expounds the composition of green roofs, the internal mechanism of green roof ecosystem functions, reviews the green roof ecosystem functions and policy promotion effects and the prospect is put forward from the research status of the green roof ecosystem function and the policy promotion effect. The research field of green roof mainly focuses on the service effect of environmental regulation. In terms of water environment regulation, most studies are about the water environment regulation function of green roofs. It is necessary to further explore from the perspective of the water cycle of green roof ecosystems, and to clarify under what circumstances green roofs are runoff pollution sources. A problem that needs to be solved urgently. In terms of thermal environment regulation, most studies focus on quantifying the impact of green roofs on urban thermal environment, and there is still a lack of a comprehensive understanding of the mechanism driving the cooling effect of green roofs, which is also one of the difficulties in the study of thermal environment regulation functions. In terms of building energy consumption, the physical parameters of green roofs required for building energy performance modeling are still lacking. It is necessary to construct an energy transfer model from long-term observation data to clarify the energy flow difference between green roofs and bare roofs. From the perspective of building-substrate-vegetation-atmosphere, we need to comprehensively study the process mechanism of green roof energy flow, and clarify the difference between actual building energy consumption and simulated energy consumption. In terms of policy promotion effect, policy promotion is the main driving factor for the popularization of green roof. Compared with Europe and the United States, the promotion of roof greening policies in my country is relatively single, and there is a lack of promotion policies covering the entire roof greening life cycle. We can learn from Europe and the United States to promote the construction of roof greening in multiple dimensions and on a large scale, and increase promotion efforts, in order to improve the urban environment.