City joint is used to describe urban space in the urban study, and it was first put forward as one of the five key elements to representing city's image by famous American architect Kevin Lynch in 1960s.From then on, the diversity of city joint has been emerging due to different understanding of this concept.However, systematic study on city joint is very insufficient at the moment, and the concept of city joint is combed and clarified, and its space domain is investigated, in order to provide a reference to solve current situation problem in the modern urban construction.