The principle scientific basis of this paper is the Semiotics. Semiotics is a new approach in the literature which has been launched for the first time in France in late 1980s ‘.This newly settled notion, studies sign and meaning in a reciprocal relation and as many approaches in linguistics and literature, could be used as a tool for analyzing subjects in various disciplines like science, philosophy, and sociology. For this exact reason, planning and urban design could borrow it as a method of analysis in the sign-meaning domains of the city. Language is a coherent system and its subsystems or subordinate levels are reciprocally connected either in their form and content. Content needs two different structures to become tangible: syntactic and semantic. Syntax and semantics are very close and their confrontation is nothing but a kind of inter relation. Syntax is an objective process through which meaning comes into reality and semantics is a searching procedure that seeks the meaning where the signs are mutually related and woven together. Cities are full of signs and meanings that indicate to them. The main feature of sign-meaning system is its flexibility and fluidity. This feature is visible through the time and continuous metamor phoses of urban structure. Therefore, it’s quite possible to recognise series of production, reconstruction, omission, alteration and variation of signs and meanings by an analysis based on Semiotics principles. In other words, the city, like the dialogue in linguistics, could generate a flexible sign-meaning system that because of its flexibility produce new sign-meaning structures at their turn. A Semantic field, whatever its scale might be, shows degrees of meaningfulness which has been influenced by a variety of economic, social and political issues dominating the urban text and context. Each semantic field changes in form and content by the change, omission and addition of its words and subsidiary elements. So by occurring changes in form and content of semantic fields, meanings may change considerably or new meanings may appear. This form-content analysis methodology is tested in a case study work. The case chosen for this reason is the ‘Canon Square’ (Maydan-e Tupkhaneh) of Tehran, a historic urban space of Iran’s capital. This space has been chosen just for testing the ability of this methodology and the aim was not to explore the whole or partial historical evolution of a city. This field also could be studied in bigger or smaller scales going from some blocks as a main structure or even an small urban space. As the evolution of Maydan-e-Tupkhaneh has been the subject of some researches, it helps to avoid the explanations not necessary for the paper and lets the methodology, taking into account the results of those previous researches, go directly to the form-content analysis of the space by synchronic and diachronic dual approach. This paper is an initiative for the author to find a methodology proper to similar analyses. Further and broader research may establish a complementary method to those of form-content analysis.