Today, some urban parks are not very sociable and lively despite paying attention to environmental issues, and even in some cases, they have been raised as problematic spaces. For this purpose, the purpose of this research is to investigate the role of flexibility and its effect on sociability and vitality and to identify the contribution of each of the factors affecting the urban space in the realization of a successful public space. Also, the current research is descriptive-analytical research in terms of its nature, and in terms of time, it is a prospective cross-sectional research, and in terms of its purpose, it is part of applied research, and in terms of process, it is considered part of quantitative method. First of all, the current research is non-experimental, secondly, these researches have different models, some of which are only for description, some other researches, in fact, this research is part of this category, are of the correlation type. In this type of correlation studies, relationships between variables are investigated. Also, the sampling method in this research is the test-making method, in which approximately eleven people were selected for each item; The number (464 people) was set as a sample and criterion, and a questionnaire was distributed among this number of citizens. Data analysis was done through correlation and regression, structural equations in Lizrel, Spss software. The results of the research showed that National Park has average conditions with sociability (3.17) and flexibility (3.01); And with the vitality score (2.86), it is not lively. Also, as the vitality of the urban space fades, the spaces take on the color and smell of a silent space, and over time, other components of success in the space also lose their ability, and thus the urban space becomes a space just for passing. But the researcher's solution is to take the public space out of the silent state and achieve a sociable and successful space through strengthening and upgrading the vitality index and with a catalyst called flexibility.