Today knowledge of urban spaces and suitable urban design of them is a way to meet the diverse needs of citizens. In the meantime, consideration of the principle of flexibility as one of the factors creating quality urban space enables space to provide the numerous options to citizens. However, in this study, which has an exploratory nature, attempted to explain the concept of flexibility and ways of its realization in the urban space, and also a model is presented in order to achieve flexibility in the urban space. The attainment of this space, with the flexibility indices first need preconditions, which include permeability, diversity, and readability. For this purpose, first qualitative data was collected using library studies and a review of the literature, the most important elements involved in the flexible design of urban space were identified; then by Delphi method, and by means of a questionnaire, and based on the snowball method, components were measured. The results indicate the more effective roles of 17 indices in the formation of flexible urban space. According to the ranking table, indices of compatibility of performances, flexibility, and more choice and greater attention to human relationships and access were more important.