According to the modernization and urbanization changes, some of post urban spaces missed their utilization and structures. They have been destructed and forgiven completely. The castles and defensive fortifications are among those spaces which have a parted structures from the urban contexts. Their structural and utilization erosion has turned them into the ruined and criminal places. The first step to regulate these buildings are recognition of these buildings. These buildings were classified according to their initial utilization in province of Yazd. In this research, the castles were divided to five classes such as: governmental, residential, military and disciplinary castles, depots and stores, citadels. The results of studies reveal that citadels include the most abundance (10 buildings) in geography province of Yazd. The depots and stores and state castles (7 buildings ) are in the next ranks. The military and disciplinary castles (4 buildings) are in the next rank. In last rank are the residential castles (2 buildings).