Abstract: The impacts of climate change on urban flood, urban heat island and lack of farmland according to rapid urbanization are expected to widespread and severely influencing to socioeconomic conditions. The green roof system within cities is now recognized as a means of alternative solution to urban flood, heat island phenomenon and producing food. In this study, the concave green roof and normal roof are compared on the #35 building in Seoul National University, Seoul, Korea. The objective of this study is to validate effect of (1) urban flood mitigation, (2) reducing urban heat island and (3) producing food. For the effect of urban flood mitigation, the concave green roof system retains and stores the rainwater in soil and 10cm side wall. The concave green roof system of which area is 140m² showed effect of flood mitigation reducing peak flow quantity of 56%, peak time delay of 3 hours and storing rainwater of 10~40 ton. For the effect of urban heat island mitigation, the temperature difference of 27 °C was monitored comparing to the normal roof. For urban agriculture, this green roof (420 m²) is managed over 30 households near campus. In this roof garden, various types of crops (e.g., vegetable, root crops, and fruits) are achievable. Also, this can make contribution to local citizen food security and social community development. Many creative and innovative activities were made possible at the green roof by the community such as musical concert, community lunch, green product donation movement, etc.By applying green roof system on the buildings, without destroying existing urban infrastructure, there will be environmental & economic benefits and place for urban farming can be secured where people can improve not only their food self-sufficiency but also social community activities. Thus, Based on this successful project, Seoul Metropolitan Government is planning to make a guideline for green roof promotion.