The book The Laws of Duwan of Mamati's Son (T, 606 E) His approach to his narratives is a topic of historical and civilized importance. The Fatimid Age of the People of Jehovah has expanded its influence and authority, including ministers, writers, doughnuts and foreshores. One of the Christian families that shined in the late Fatmi era was "Mamati", who lived in "Assiut" from Upper Egypt, then moved to Cairo, and enrolled in the service of the Fatimids, where their sons held important positions in State offices.Ibn Mamati became in charge of the Army Office and then added to it the Finance Office, which became the most important downs in Egypt. Through his work in the Duwan Law Books, this book was a living record of the Dawawans in the Ayopean State. The study of the book is important because it is one of the first-class documents that bears the qualities of this known kind of great encyclopedia that emerged in the Middle ages. The research aims to study the methodology of Ibn Mamati in his book The Laws of Downs, the methodology by which the author singled out that he was combining theory and practice because he worked in the Duwain Register and at the same time is a high-class historian so he produced this classification for us with that precision and that classification to be calculatedThis research involved researchers who were the first researcher concerned with the name and lineage of the son of Mamati, as well as a brief presentation of his book The Laws of Downs. AMA Research II: He focused on his approach to his book The Laws of the Downs, which included 15 axes of his curriculum that dealt with the various axes of systematic, historical, cultural and economic activities and then the conclusion, sources and references. The main point of the research is that Ibn Mamati has expanded his approach to historical, economic and administrative issues such as, for example, feudalism and its types as well as agricultural and animal production and financial resources of the Ayubian State