Dunhuang topography were found in the three pieces of writings of Dunhuang Manuscripts in the collections of London and Paris respective: S.788?S.5448?P.3721. The three pieces of Dunhuang Manuscripts had recorded a story about ZHANG Xiao-song who had killed a dragon at a place near Dunhuang(then known as Shazhou) named the Spring of Jade Maid and this story had prevailing in Dunhuang for a long time and it was gradually grown more and more perfect in plot and complete in detail and had become very familiar with the local folks. With a profound historic background, it was found to be started from ZHANG Huai-shen, then the second generation of Dunhaung Governor, who had made false claims of that they were the offspring of ZHANG Xiao-song, therefore, the prestigious clan of ZHANG family had taken a shift from previously claimed 'origin of ZHANG Family of the Qinghe River' to 'the origin of Nanyong ZHANG'. By a careful study, this article viewed that the event of change family name had taken place for a political purpose. By the time that the event had taken place while ZHANG Yi-chao, then the first generation of Dunhuang Governor, was dead leaving the governor position in blank, ZHANG Huai-shen had no other alternative than to get his commission as the new Dunhuang Governor from the Tang Court, he was so urgent to making a request for a decorated staff used by ancient emissaries as credentials and the officially rank of governor conferred by the central government of the Tang Empire.