Against the background of the most significant historical events of the era of Genghis Khan, all stages of the process of formation and evolution of the state-legal system of the Great Mongolian Ulus are reconstructed, the reader is presented and commented on almost all fragments of the “Book of the Great Yasa” of Genghis Khan, which have come down to us from time immemorial. Particular attention was paid to the military-political doctrine (Mongolian Tengerism) reflected in the “Book of the Great Yasa”, the new concept of international relations of the Great Mongol Ulus and their implementation during the reign of Genghis Khan (1206–1227). The appendix describes the action “ Books of the Great Yasa" in the post-Genghis Khan era on the territory of Rus', which in the XIII-XV centuries. was part of the Golden Horde Khanate. A popular science publication designed for legal scholars, historians, religious scholars, as well as students, graduate students, teachers and researchers of universities, as well as for all readers interested in the history of the life and work of Genghis Khan. Dedicated to the 860th anniversary of Genghis Khan.