Quantifying the performance of national policies and programs in different economic, social, and environmental fields has always been a major concern of planners, politicians and researchers worldwide. According to UN statistics, more than 60% of the world population will live in urban areas by the year 2030Despite occupying only 2% of the total land area on Earth, more than half the world's population is living in cities. In this study, a systems approach was adopted to develop a composite index  in order to assess the potential of a city to become sustainable. The index is composed of 10 components containing a total number of 19 indicators. According to which, the 22 districts of Tehran City were compared in terms of sustainability of urban environment quality. The obtained results indicated that the Districts 1, 2 and 3 are in ideal sustainability conditions. These areas are among prosperous places of the city. About 59.09% of all districts were below the average. The Districts 18 and 19 with the values of 0.21 and 0.25 remain in critical condition.