This study aims to find out the truth of al-calipha AL-mamon's attitude and his policy towards Al-alaween. Also, it aims to follow Abi Al-saraya Al-Sari Al-Shebani's movement in Iraq and it's expansion in Al-Hejaz and Al-yemen. In addition, it looks for the reasons behind the change in Al-Abassi's attitude towards Al-alaween in Al-mamon's era. Move over, it shades the light on the character of Imam Ali bin Mosa Al-Redah and his position in Al-Mamon's period, and the reasons which let Al-mamon makes the homage for him, and the eco of that homage and it's concequences in the political field. This study depends on analytical and inductive method. First, it depends on reading various novels which were published by different sources. Then, through analyzing and comparing between Al-Sunni and Al-She'a's sources. Finally, following Al-Abasi and Al-Alawy's opinions as well as historian's apinions, about the policy of Al-calipha Al-Mamon to wards Al-alaween. This study is divided into preface in order to given a general idea about the relationship of Al-Abassi and Al-Alawyi before calipha Almamom era. Then an introduction includes some previous studies and analysing to some essential resources which have a direct relation to the topic of the studay. Also, it has three chapters and a conclusion which includes the important results that the researcher has obtained. The first chapter reviews Abi Al-Saraia Al-Sari Al-Shebani's movement in Iraq. Whereas, the second chapter concentrates on the expansion of his movement in Al-Hejaz and Al-Yamen . The third chapter describes the relationship between Al-calipha Al-mamoon and Imam Ali bin Mosa Al-Redah and the reasons which make Al-mamon has agood relationship with him as a result he make the homage for him. Also, this chapter clarifies the impact of Alcalipha Al-mamon policy in isolation toward Al-alaween. The researcher finds out a number of important results. The most important one is that meaning of Al-calipha Al-Abasi Al-mamom in marw" for along time makes people frustrated. As a results, Al-Alwyeen seize this opportunity and the suitable time to take revenge from AlAbassi in order to take their position. More ever, the researcher finds out that the assignment of Iman Ali bin Mosa Al-Redah considers as maneuver from Al-Calipha Al-mamoon to threat Begdad and all Abassi to accept him.