The article describes the composition of Tuvan ethnic groups from the Buyant somon of the Khovd aimag in Mongolia, who moved to that area in 1930-1940 from the territory of the Xinjiang Uygur Autonomous Region of the People's Republic of China. Data about the number of representatives of various clans at the present time, the territory of their settlement, historical information about the inclusion of the considered ethnic groups into one of three Tuvan khoshuns of the Altai Uriankhians are given; field materials containing information on the origin of irgit, khaa-dargan, khöyuk, chag-tyva clans are presented. It is shown that the main difference between ethnic groups is the predominant type of their economic activity: chag-tyva (hunting), irgit (cattle breeding), dongak (blacksmithing).