Since the 1940s, the military administration of the Old Tibetan Empire (c. 600-842) has been studied by scholars such as Giuseppe Tucci (1949) and Sato Hisashi (1958-59). These studies have clarified the basic structure of the military system in Central Tibet, such as the ru and the thousand-district (stong sde). However, the subordinate units of the thousand-district are yet to be scrutinised. Takeuchi Tsuguhitoʼs pioneering work on the subunits of the thousand-district in the Tibet-ruled Dunhuang (Takeuchi 1994) revealed the basic function of the subunit tshan. However, there are several other subunits such as brgya-tshan, tshan, bcu-tshan and khram-tshan which are yet to be studied. This paper re-examines the basic structure of the thousand-district during the Old Tibetan Empire. The author analyses several subunits of the thousand-district and their organisation by mainly drawing on Old Tibetan and Chinese texts from Dunhuang.