Abstract: The current international frontier researches on roof greening indicate that comprehensive environmental efficiency of urban greening and ecological environment of roof greening has attracted increasingly higher attention. With the whole life cycle analysis of green roofs, we put forward the research-oriented design of green roofs based on environmental efficiency “pre-study, deepening design and effectiveness evaluation”. We applied the design method to the practical case of Joy Garden to simulate its wind environment and sunshine. According to the simulation results, three schemes are preliminarily designed. We evaluated and determined the best scheme from the perspectives of safety, environmental benefit and whole life cycle, and further deepened the design based on the environmental efficiency. The effectiveness evaluation results after project completion show that the roof garden in the case plays an active role in improving the environmental efficiency, such as building energy conservation, rainwater management, improving urban thermal environment and increasing urban biodiversity.