Urbanism in Iran in Sassanid period have a considerable evolution. Although urbanism in this period has its root in previous periods, but the Sassanid city from city body point of view and periodical function has experienced an evolution and development and some parts was added to it. There are some factors which influenced on urban development of Sassanid city and in this paper 4 of dimensions of it namely political, social, cultural and economical factors which are influential in this evolution has been studies; therefore, the aim of this paper is to describe historical characteristics and analyze the main elements of the urban society of Sassanid period from the point of view of role and effect of political, social, cultural and economical trends which have influential in this regard. Studying this matter by describing and historical analysis shows that Sassanid city with political, military and central government domain has found a deeper consistency comparing to the past periods. Also the urban society and the body of the Sassanid city has been under the influence of religious teachings, social ideals and worldview of that period.