Any spatial organization with the ability to make internal changes can answer extra demands of its users at different times. Therefore, it can possess a better performance than to the performance of single-functional spatial organizations. The main purpose of this research is to measure the flexibility of spatial system of houses using the space syntax in three traditional, traditional-contemporary and contemporary patterns in Qazvin. To achieve this goal, on the one hand, various manifestations of the flexibility of the spatial system of the house and, on the other hand, features of the space syntax were identified based on valid books and papers; Subsequently, flexibility expressions were evaluated and analyzed with a number of architectural concepts related to space syntax through descriptive-analytical and logical research method. In the present research and in this theory, the measurement tools are the justification Charts, the DEPTH MAP software and the data extracted from these two. Results of the research indicated that the influence of the spatial system on the development of the traditional houses was much higher than traditional-contemporary and contemporary instances. Also, most of contemporary houses, regardless of their construction area, possess the equal rate of flexibility in their spatial system. However, with a change in construction area in houses of traditional and traditional-contemporary era, the flexibility will face change.