Administrative institution as one of the requirements for the continuation of the political structure of the state played a role in establishing the authority of the Umayyad and the Abbasid (the first era) Caliphates. With regards to the development of the administrative system in the Umayyad period, the continuation of the Umayyad power for almost a century and the evolution of the administrative system in the Abbasid era, this study explores the role, impact and interaction between bureaucracy and political authority in the continuation of the Umayyad and Abbasid Caliphates' power. The findings of this study, which was based on an analytical-descriptive approach, using Weber's concept of traditional authority, show that by imitating the administrative system of the Sasanian and Byzantine empires, Umayyad government adopted a Patrimonialism profile. However, the internal problems, religious differences and social inequalities were the main obstacles for promoting bureaucracy in this period. While in the Abbasid government due to the authority of the Caliph, tasks division, institutions expansion, focused administrative system and control over the bureaucrats were developed and expanded;  a governmental approach which was called Patrimonial- Bureaucratic system by Weber.