In February 1221, Changchun left, traversing modern-day eastern Mongolia to the camp of Genghis' youngest brother Otchigin near Lake Buyur in the upper Kerulen – today's Kherlen-Amur basin.

From there he traveled southwestward up the Kerulen, crossing the Karakorum region in north-central Mongolia, and arrived at the Altai Mountains, probably passing near the present Uliastai.

After traversing the Altai he visited Bishbalig, modern Ürümqi, and moved along the north side of the Tian Shan range to Lake Sutkol, today's Sairam, Almaliq (or Yining City), and the rich valley of the Ili.

Finally, through the Iron Gates of Termit, over the Amu Darya, and by way of Balkh and northern Afghanistan, Changchun reached Genghis' camp near the Hindu Kush.

From the narrative of his expedition, Travels to the West of Qiu Chang Chun written by his pupil Li Zhichang,[15] we derive some of the most vivid pictures ever drawn of nature and man between the Great Wall of China and Kabul, between the Aral and Yellow Seas.

By order of Genghis Khan, some of the former imperial garden grounds were given to him for the foundation of a Taoist Monastery of the White Clouds[5] that exists to this day.