The book of "Istigamma" - the Straightness - by the author Abu Saied Mohamed bin Said Al-Kodmaj is one of the most greatest Islamic, Omani books. The book explains matters of "Baraa" and "wilyaa" and its issues. The book was written after the occurrence of disorders raised on the resignation of Imam Al Salat Bin Malik the Imma at the time when Mousa Bin Mousa and Rashid Bin AL Nadir rebellion. The author investigated the case and provided the evidences and discussing the argued issues. Then replied to the disagreed says. He also, has provided other religious issues. - The thesis comprised of a study and investigation of the 1st part and ind part of documentary book which I have classified them in two sections. Where the first part contained two units, the first about the author Al Imam AL Kadami and Istigamma book and contains two units the first about the conditions in Oman during the era of the author life such as its family, childhood, his birth and death times as well as his followers, collections and his books, as well as characteristics, and charisma and his social, academic positions among the religious men. The second unit aimed for definition of Istigamma book and the methodology of analysis whereas the first topic of it included the study of book in the matter of name, objectives and goals of writing the book and the methodology being followed by the writer, besides to the intellectual value of the book. The second topic was about inspiration and mind from the view of Imam AL Kadami. The third topic was included the investigation methodology and its priorities, then a list of its keys submitted to it besides to documentation and essential pictures from the book. The second part of the thesis was about investigation of first and second units of the documentary books. Started from chapter one up to chapter Nine, whereas a scientific methodology being adopted for it. The conclusion comprises most important results and finding came out from this thesis accompanied with Quran verses and Sunna of Hadieth as well as the contents and references and resources.