Abstract:Yadong area of Tibet Autonomous Region, China locates in a wedge junction of the South slope of the Himalayas of China, India, and Bhutan. And it is an important frontier of defence area and trading port from time immemorial. Under the background that India provoked the dispute in the Donglang border, clarification of the historical change of the boundary of Yadong area and analysis of its geostrategic position can provide a beneficial decision support for the construction of the Belt and Road Initiative and the safeguard of Chinese border's security. In this paper, historical materials, historical map, and GIS technological means were comprehensively used to analyze the historical change of the boundary of Yadong area and its geostrategy. The results were shown as follows. Firstly, the boundary change of Yadong area experienced four stages in the historical period. And it was closely related to the geopolitical pattern of the surrounding area. Donglang area is the inherent territory of China from time immemorial. Secondly, geographical factor, especially watershed, is never the only basis of the boundary division. Historical tradition and the border convention must be respected. Thirdly, breakthrough the geographic limit and strengthen the geopolitical influence of Yadong area would be the significant strategic choice to suppress Sino-India buffer area and eastern and western border, overlook the Siriguri corridor, and counterbalance the challenge that comes from the southern Asian and Indian Ocean area.