According to the New Town Development Plan, Gang-buk area, a symbol of slum in Seoul will be changed new residential area. There are a lot of challenges for success this project. First of all, new ways of city plan "pre-plan and development" and "environmentally friendly development" are necessary to carry out this plan. Another important idea is how to overcome conflicts such as unbalanced development, a traffic jam and environment problem. Also, Government and a citizen agree that this project have to accept eco-protectable and sustainable development theory. For increasing green area ratio and keeping eco-diversity, planting at roofs and water circulation system in residential complex are compulsory. Green network based on environmentally friendly development provides a natural energe stream on eco-system and protects a city from air pollution, hot air island phenomenon and a flood.