Abstract: Space syntax can be an angle to study the space form scientifically. Space form can be abstracted as the objective data to express the relationship between the space and human behaviors. Taking Taigu ancient city as an example, the authors aim to analyze the street space form using Depth map software, based on literature data and survey data. By choosing the map of Ming and Qing dynasties and the map of status quo as the research objects, the street space form in ancient city was abstracted into an axis model and a line model. The eigenvalues of integration, intelligibility, selectivity and entropy were obtained for describing the characteristics of space form. According to different space forms, the corresponding landscape design methods were adopted. Comparing the spatial eigenvalues of the two periods, the method of space syntax was introduced into the study of the space form development mechanism, which could provide reference to ancient city protection and develop the landscape design for Taigu ancient city.