Dartsendo (Dar-rtse-mdo in Written Tibetan), generally known as Kangding, is a town in the easternmost Tibetosphere, located in Ganzi (dKar-mdzes) Prefecture, Sichuan, China. This town has played an important role for the tea-horse trade since the Ming Dynasty, and is inhabited by both Tibetan and Han Chinese. Under these circumstances, extensive language contact has existed for a long time. Dartsendo Tibetan is the Minyag Rabgang vernacular of Khams Tibetan, and it was once considered as a lingua franca-like variety in the Minyag Rabgang area. However, Dartsendo Tibetan is currently facing extinction. This paper will discuss: (1) the historical background and language situation in Dartsendo, (2) the current language situation of Tibetic languages spoken in the centre of the Town, and 3) the process of endangerment of the local variety. Based on these descriptions, this paper will also propose a method for identifying endangered varieties in the Tibetic languages.