This study is an attempt to scrutinize the impacts of the urban expansion on the green space of Tehran. During the last two centuries, Tehran extent has increased from 5 kilometer square to 750 kilometer square, which is about 150 times greater than before. At the same time the population of Tehran has increased from 15 thousand people to more than 7 million peopleÃ?Ë?Ã?Å? amounting 400 percent growth. Current study is investigating on quantitative characteristics of Tehran green space by means of geographic information systems. In order to get to this object the information of Tehran population and its green space has been collected and by using GIS soft ware and map overlaying and also comparison of current situation with global standards final result has been reached. Green space development in Tehran has an increasing trend. The number of parks has been increased in Regional and local scale but the important point is the unsuitable distribution and dispersal of public green space in Tehran some Districts like (4,7,8,10,11,12,13,14,16,20,21) have the least green space per capita (less than 4 meter square).In addition to this, discussing spaces have been distributed improperly and they have low social and ecological efficiency. Finally, from comparison of four existing standards about ideal urban green space with Tehran green space in current situation (sum of green space consisting parks and afforestation is equal to 6.4 square meter) we came to this result that in order to get to green space equal to 12 square meter per capita according to the ministry of housing and urban development standards it’s needed to develop Tehran green space about 44793002 square meters and in order to reach green space equal to 30 square meters per capita which is the standard of united nation it’s needed to meet lack of urban green space about 169,943,706 square meters in Tehran city.
