The principal part of the British Collection of Dunhuang Manuscripts from the Library Cave(Cave17) is composed of circ. 230 bundles which were purchased secretly by Stein at distant Anxi(now Guazhou) in early October, 1907. The number of documents acquired in this third batch of manuscripts is far greater than the first and second batches, a total of circ. 140-150 bundles, purchased secretly by Stein at the Mogao Grottoes respectively on 28 May and 6 June, 1907. Researchers on the origin of the British Collection of Dunhuang Manuscripts have so far focused their attention only on Stein’s purchasing activities during his stay in the Mogao Grottoes from 21 May to 12 June, 1907. On the basis of some of Stein’s personal papers preserved in Oxford, this article deals especially with the background of Stein’s third secret purchase of Dunhuang manuscripts at Anxi in early October, 1907 as well as the smuggling procedures subsequently used to secure them.