The paper sets out to compare two widely applied planning strategies--- green belt and green wedge--- to understand if as an alternative, the green wedge has more strengths than green belt. Green belt has long been the planning policy with a steady position in UK, and also accepted by other countries, Australia, Japan, Korea for example. But during recent years, this policy has been under accusation for fostering un-sustainability, housing shortage and value degradation of the green space. A reform of the existing green belt policy has been advocated by researchers. While on the other hand, the green wedge somehow shows its capability at meeting the demands of regional development. A comparative case study between London which has the most famous and original green belt and Stockholm which represents the application of green wedges, is chosen to understand their different strengths and weaknesses. The comparison covers regional level, city level and ‘green’ level corresponding to the three problems mentioned above respectively. The outcome suggests that green wedge does have some merits over the green belt in dealing with the needs of expansion of urban area. Green wedges are found to be more sustainable and flexible. Besides, the green wedges of Stockholm have higher values at social, ecological and economic levels and with better accessibility. Even though the green belt seems to be untouchable as a planning policy of London, I come to the conclusion that splitting the green belt into wedges can be taken into consideration to provide better access to green space while allowing for more coherent urban growth.