The Han Dynasty is preparing to wage war against the Huns. By chance, Emperor Wu of the Han Dynasty learned from the mouth of a Hun prisoner that there was a Yue kingdom in the Western Regions, whose king was killed by Hun Khan and his head was made into a wine vessel. The Vietnamese couldn't stand the slavery of the Huns and moved to the Ili Valley at the northern foot of Tianshan Mountain. It was attacked by Wusunguo and then moved southwest to Guishui (now Amu Darya) basin. Wang Yue wanted to avenge his father, but no one helped him. Liang Wudi, after understanding these situations, wanted to unite the Yues to "break the Hungarian right arm". So I decided to send a special envoy to Dayue. Zhang Qian was recruited as a Langguan, shouldering the heavy responsibility of going to Ren Yue.

In the second year of Jianyuan (BC 139), Zhang Qian led Hunganfu and more than 100 people to set out from Longxi (now Gansu). They stayed at dusk, camped out in the wind and tasted hardships. Unexpectedly, they were captured by Xiongnu halfway and escorted to Xiongnu Wang Ting. In order to win over and soften Zhang Qian, the Huns married him and gave birth to a son, which lasted for ten years. However, these did not shake Zhang Qian's determination to complete the mission of communication with the western regions, and the continuous festivals he brought were always with him.

One dark night in a month, Zhang Qian and his party escaped from the Huns while they were unprepared. They entered Yanqi (now Yanqi area, Xinjiang) via Cheshi State (now Turpan Basin, Xinjiang), then traveled westward from Yanqi to Tarim River, passed through Qiuci (now Kuche East, Xinjiang), Shule (now Kashgar, Xinjiang) and other places, crossed the green ridge and arrived at Dawan (now Feigana Basin). Under the guidance of Dawan's guide, we arrived at Kangju (now between Balkhash Lake and Aral Sea) and finally arrived in Da Yue.

However, Da Yue's national conditions have changed greatly. After they moved to Guishui Valley, they conquered the neighboring country Daxia (now northern Afghanistan) and decided to live and work here, and they didn't want to fight Xiongnu again. At the same time, the Vietnamese thought that the Han Dynasty was too far away from them to unite to attack the Huns, so Zhang Qian's goal of "breaking Hungary's right arm" was not realized. Zhang Qian traveled to Daxia and other places for more than a year and set off for home in the first year of Yuanshuo (128). On the way home, in order to avoid the Xiongnu-controlled areas, Zhang Qian changed to the south road. They crossed the Green Ridge, along the northern foot of Kunlun Mountain, passed through shache (now shache, Xinjiang), Khotan (now Hotan, Xinjiang), Shanshan (now Ruoqiang, Xinjiang) and other places, and entered the Qiang people's settlement. But it was seized by tarquin on the way and detained for more than a year. In the third year of Yuan Shuo (BC 126), the Huns were in civil strife, and Zhang Qian fled back to the Han Dynasty with his wife and assistant Gan Fu. Emperor Wu of the Han Dynasty was very happy after hearing his detailed report on the Western Regions. He was appointed as a doctor in Taizhong, and his father was appointed king. Zhang Qian came to the Western Regions uninvited. Thirteen years later, he traveled all over Tianshan, Central Asia and West Asia. He was the first person from the Central Plains to the Western Regions.