This study aims at exploring the history of the Omani Navy during the time of the Yaarubi reign from 1059 / 1131H to1649/ 1719AD in order to recognize the political situations in Oman before the setup of the Yaarubi reign and the emancipation of Oman from the Portuguese conquest we will also shed light on the military point of strength in the yaarubi Navy and the sea battles between the yaarubis and the Portuguese in the Arabian Gulf, the Indian ocean and Eastern Africa. The researcher divided the study into an introduction and three chapter in which he explored the present situations in Oman before the setup of the yaarubi reign Through demonstrating the 2nd Nabhani state and its rulers. Then,he moved to the Portuguese invasion of Oman in 1507Ad ,and then the setup of the Yaarubi state , unifying Oman and the beginning of the struggle against the Portuguese . The study explained the setup of the Omani Navy in the Yaarubi reign exploring the factors of settling up the Navy , its points of strength, Ports where ships are made and the wood used in this industry. then , he showed the Omani Navigation art at that time, the work procedures on the ships , the salaries , the loans , the cost of voyages and distributing shares . Then the study moved on the Omani Portuguese struggle in the time of the Yaarubi in the Arabian Gulf, the Sea of Oman , the Indian Ocean and Eastern Africa until the loss of Mombasa . It also shed light on the foreign relationships of the Omani Navy at that time. Conclusions : 1- The Portuguese invasion of Oman was a main reason of setup of Omani navy. 2- Omanis strategic location and its human and natural resources contributed greatly to setting up the Navy. 3- The Omani Navy became so strong that it was feared by international navies. 4- The Omanis became greatly skilled at making ships , knowing the seasons of sailing and the sea routes. 5. The Omani Navy archived glorious victories on the Portuguese in the Arabian Gulf, the Indian ocean and Eastern Africa.