The distribution patterns of Parthian and Sassanian settlements in Damghan and Shahrood plain with their defensive and environmental landscape would be argued in this paper. According to the result of archaeological fieldwork in Bastam (Farokhnia, 1395) (Roustaee, 1383), Shahrood and Damghan plain (Trinkaus, 1981) , most of the parthain and Sassanian settlements were located in the low slope of the plains and close to the some water features such as Qanats. They also are very close together and were located in the middle parts of the plains, because of the better subsistence conditions. The settlements might be the small scale societies (small villages) which were clustered close to the main roads. However organized defensive structures, economical and industrial evidence are the distinctive characteristics of the settlements in the neighborhood areas such as Gorgan and Khorasan, there are not the same evidence related to these settlements in these plains. It’s apparently the settlements were defended by local strategic. The distribution patterns of settlement demonstrate more nucleated and in some parts of the area they distributed sparsely. Nucleated patterns might be applicable for defending settlements together and to be more resilient. Interestingly enough, the settlements in the late Sassnian were formed more sparsely and they are not nucleated anymore. I would argue the settlement patterns probably shows the societies were not involving with the conflicts and tensions. They might be more in the peaceful condition. Also Parthian and Sassanian settlements might would be a camp sites or small villages which were not strong and organized enough to establish defensive systems.