About the historical interpretation of contemporary Tibetan, approximately can find the basic proof through the historical background of the Chim-Kham-Tsang Plateau and its peripheral areas. From the Ti and Ch’iang peoples of pre-Ch’in period to the Tu-fan (Bod) of T’ang Dynasty, the ancestors of contemporary Tibetan had formed gradually its basic predicament of ethnicity and cultural content. Nevertheless, there are more than four millions “Tibetan Nationality” in modem China, this phenomenon basically can have been considered as a special result of PRC’s policy to ethnic identification in 1950s. Historically, there is a very close interacting relation between contemporary Tibetan and other Sino-Tibetan language peoples in the Chim-Kham-Tsang Plateau and its peripheral areas. However, in this historical process, part of small ethnic groups have had to “ be fused but not completed yet” with the Tibetans that around them. This result inevitably has been caused some controversial discussions about the accuracy of PRC”s policy to ethnic identification. According to these reasons, this article would like to use the viewpoints about historical interpretation of Tibetan’s ethnic formation, and by means of a small ethnic group: the “Baima-Tibetan” in the border areas between Sichuan and Gansu, to analyze the process and meaning about this people who declared to sever its relation with the category of Tibetan and try to establish a new ethnic terminology- “Ti Nationality” in the end of 1970s.