Abstract: The Toyo Bunko owns some collections of the valuable archives of the Bordered White Banner Mongol Generals Yamun in Qing dynasty. For the forms, these archives can be classified as the archives of the origins of the assistant commandant, the Memorials of the assistant commandant, the archives of the genealogical tree, the Memorials of the hereditary of the positions and their genealogical tree, the archives of the introduce and complementary feeding, the archives of annual situation of the old cape’s soldiers, the archives of daily costs, the lists of the records, the Memorials of the Gratitude, the archives of the money-grain relations, the archives of submission of the assistant commandant’s widows and children etc. From the content of these archives, this paper analysis the construction of the assistant commandant members of the Eight-banner Mongolians, the genre of the Niru and the assistant commandant, the hereditary titles, the effectiveness of the decrees, the languages of the archives, and then emphasize the important historical value of these archives.