Capital is the predominant foundation of economical, political, administrative, even cultural and social affairs in history of Iran and various elements shaped the structure and administrative system of the capital. Beside geographical, economical, political, social, geopolitical and administrative characteristics of the country, cities with regard to different reasons had experienced the rank of a capital for a long or short period, while government had an important role in selection, development and structure of capitals in various basis and characteristics. Seljuk extended the geographical territory of Iranshahr (land of Iran) in Islamic period towards the borders of ancient era of Iran. The vast territory similar to Achaemenids involved the centralization of power in a large capital as the main center of government and other conjoint capitals as the smaller centers of power. Nishabur, Ray, Isfahan, Marv, Qunieh, Kerman, Hamedan, Yazd and Shiraz beside some other cities were the governance and sovereignty center of the great Seljuk, Seljuk of Anatolia, Qavardian (Seljuk of Kerman) and Atabaks. They had settled their capital system not only by enjoying the traditions and capital system in Iran as an ancient heritage transferred from government such as Buyids to Seljuk, but also by using the distribution of the power in capitals alongside with a great and palatial capital of Isfahan. This article will study the capital system of Iran during Seljuk period with an emphasis on multiple capitals of Seljuk of Kerman in order to analyze the elements and patterns of selection, body development and social, cultural, economical, administrative and political progress, the importance and the position of the cities from the capital system point of view.