Before and after the Great Wall was built, Emperor Wu of the Han Dynasty gradually built the Great Wall from Hexi to the Western Regions with the development of military forces to the west. This defense project to defend the Hexi Corridor and ensure the safety of the "Silk Road" runs from Yongdeng to Lop Nur. The main body of the project is the Great Wall, which roughly runs from Lingju North to Gulang, then from Wuwei via Minqin to Xiutuze at that time (Minqin is no longer in the northeast) and then to the southwest, via Yongchang West, via Shandan, Zhangye and Gao Tai along Heihe River and Nalin River North to Ejina Banner (Juyan in Han Dynasty). At the intersection of Beida River and Nalin River, there is also a Great Wall to the west, which runs through Anxi along Shule River and Dunhuang to Yumenguan. As for the west of Yumenguan to Lop Nur, according to the field investigation, there is no Great Wall, only a continuous beacon line. However, after Lop Nur was discovered, there was a beacon line along the southern foot of Kuruktag Mountain, the northern bank of Peacock River, and the ancient Silk Road from the desert to Korla in the northwest, all the way to the northwest of Kuqa. The structure of beacon tower is similar to that of Gansu.