With the jingle of the camel bell in Han Dynasty, China established contact with other nations outside on the Western Regions. Since then, Chinese and foreign cultures have clashed and mixed. In the time of Emperor Wudi, Hun in the north often harnassed the boundary of Han. Meanwhile, they also controlled several small states in the Western Regions. In 138 BC, Emperor Wudi sent Zhang Qian with a delegation of over 100 people on a diplomatic mission to the Western Regions to seek allies, preparing for an attack of Huns in two sides. Unexpectedly, Zhang Qian was captured just as he left Han territory, and was held prisoner for a dozen years. During this period, he learned Hun language, and got to know well the geography of their territory. Ten years later, Zhang Qian escaped and found the west-moved Dayuezhi. He lived there for a year and got familiar with the circumstances of the Western Regions. Later, when he learned Dayuezhi had no intention to seek revenge, Zhang Qian made his way back to Chang'an, with only one companion left of the 100 who had set out.

In 119 BC, Emperor Wudi sent Zhang Qian on a second diplomatic mission to the Western Regions. This time, he had an entourage of 300, with thousands of head of cattle and sheep and a large amount of gifts. They visited many countries, and these countries sent envoys with tribute to the Han court. From then on, Han Dynasty had frequent contacts with the countries in the Western Regions, later setting up a Western Regions Frontier Command in today's Xinjiang Uygur autonomous Region, which was under the administration of the central government.

The Silk Road was another outcome of Zhang Qian's journeys. The Silk Road started from Chang'an in the east and stretched westward to reach the eastern shore of Mediterranean Sea and the Roman Empire. Trade caravans from China carrying large amount of silk fabrics exchanged merchandise with traders from Persia, India and Rome, and brought home walnuts, grapes and carrots from abroad. In the following several centuries, Sino-Western exchanges mainly characterized by the silk trade were mostly carried on through the Silk Road.