This article discusses how the first Islamic government was formed and how Muslim Arabs copied the public office patterns of Iran as a model. For the first time in the reign of Omar and then after conquering Iran, when Arabs became familiar whit Iranian governmental organizations and tax system and observed their advantages, with the help of the expert Iranians, established the governmental offices in Islamic region. And then they hired experienced Iranian clerks to work in these offices. Up to about 82 A.H all the documents in Islamic government were written in Farsi, but in this year (65 -86 A.H), Abdolmalek - ibn - e – Marvan ordered to translate them into Arabic. Though in the first years of Islamic reign, there was just one office to deal with all financial and legal affairs and to send letters etc. with the beginning of the reign of Omavids and then Abbasids, the offices were increased in number and divided into different branches. The five major offices during the reign of Abbasids were: The ruling and seal, post, ministry, judgment and tax. The article deals with these five offices and how they were copied after the Iranian model.