The Qilian Mountains, together with the Altyn-Tagh also known as Nan Shan, as it is to the south of Hexi Corridor, is a northern outlier of the Kunlun Mountains, forming the border between Qinghai and the Gansu provinces of northern China.

Altyn-Tagh is a mountain range in Northwestern China that separates the Eastern Tarim Basin from the Tibetan Plateau. The western third is in Xinjiang while the eastern part forms the border between Qinghai to the south and Xinjiang and Gansu to the north.