The period of Imam Azzan bin Qais is considered as an important turn in political history of Oman in the second half of the 18th century as result of important events that took place at that period internally & externally especially after the death of Sayyid Said bin Sultan. Therefore, This study aims to analysis the reasons that drive the leading figures in the Omani society at the time to elect Azzan bin Qais as their Imam, Uncover the policies that Imam Government followed to deal with political, economic & social challenges of the time, & study the relation between the Imam government & the British government. Moreover, the study aims to list & analysis the challenges faced by the Imam Azzan Government that resulted in its downfall at the end. The researcher of this study deponed on the descriptive analysis method that focus on describe the information found in the historic documents & sources. The researcher uses the deductive & inductive approach in her study of the British documents to uncover the facts of Azzan bin Qais's period. The study is divided into introduction, three main chapter & conclusion. The introduction gives brief historic introduction of conditions in Oman before the election of Azzan bin Qais. The first chapter shows the personal life of Imam Azzan, his election, the rule he played in unifying the Oman tribes, his rule in stopping the Wahhabi tide & his suppression of the internal revolts. The second chapter discusses the relation between Azzan's Government & the British Government, & the effect of that in the question of recognition of Azzan's government. The chapter also analysis Sayyid Turki bin Said movement to overturn Azzan's government & British attitude towards it. The third chapter of the study focus on the internal & external reasons that result on the downfall of the Azzan bin Qais. The internal reasons were mainly the policies that Azzan took in handling his internal affairs & the external were the rule of AL Said Family & the British government. The study reached the following main conclusions: Uncovered the main reasons that led the leading Ibadi figures to elect Azzan bin Qais as Imam of Oman & followed Azzan bin Qais quest to unify Omani tribes under strong central government. It also showed the relation between Azzan government & the British government & uncovered the internal & external reasons behind the downfall of Azzan bin Qais.