The Researcher has selected the above subject in order to achieve aims such as to be acquainted with one of the most recent Hadhrami migration to East Africa and the reasons behind it. Moreover, it is also to highlight the role of the Hadhrmout Arab in the History of Al-Busaidi State in East Africa since 19th century to mid of the prin century. In addition, it is to emphasis on the Arab harmony in East Africa during Al Budaidi State. The aim of the study is also to explain the role of Sayyid Said bin Sultan in providing the wealthy environment for all groups to carry out their civilized roles in East Africa with the contribution of Hadhrmout Arab and taking over administrative, justice and educational tasks, their effective presence in the royal courts and to highlight civilization contribution in East Africa during the era of Al-Busaidi State in all social, economical and cultural aspects. Finely to highlight some Hadhrami characters which have a significant role in spreading Islam and Arabic language in East Africa. The study has been divided into three chapters. The first chapter deals with the Hadhrami migration to East Africa. The second chapter concentrates on the economical and social role of Hadhrami in the East Africa. The third and final chapter is mainly about the religious and educational role of Hadhrami in East Africa. The study has resulted in that the indulgence policy which the Omani Sultan's State has followed, contributed in the migration of Hadhrami to East Africa to conduct their civilization role in spreading Islam, Arabic language and the birth of Swahili culture. They have a significant contribution on all other life aspects such as economic, social and politics.