The large-scale maritime trade between China and East Asia, Southeast Asia, West Asia and East Africa began in the middle and late Tang Dynasty, and the main trade commodity was ceramics. The "secret porcelain" produced in the north-central region of Zhejiang Province was the main commodity of maritime trade between China and other countries in this period. According to the observations of the unearthed Chinese ceramics from various countries, the "secret porcelain" produced by the Yue kiln spread throughout North Korea, South Korea, Japan, Philippines, Vietnam, Malaysia, Indonesia, Thailand, Sri Lanka, India, Iran, Iraq, Saudi Arabia, Tanzania, Egypt and other coastal countries. The export lasted from Tang to Song Dynasty for more than 300 years. The main export port of the "secret porcelain" is ancient Mingzhou (now Ningbo) Port. The cross-border trade routes of "secret porcelain" consisted of three routes based on distances: i) northeast route, which is to the East Asia; ii) southeast route, which is to the Southeast Asia; and (iii) southwest route, which is to the South Asia, West Asia, and East Africa. There were four main reasons why China opened up maritime trade channels in Tang Dynasty: first, the Silk Road between China and West Asia was cut off; second, the "secret porcelain" traded is of high quality, in large quantity and fragile, so it was not suitable for land transportation; Third, people in Tang Dynasty have mastered shipbuilding and ocean-going navigation technology; fourth, the Tang Dynasty offered incentives to support overseas trade. The large-scale export of "secret porcelain" could improve the quality of people's life in importing countries, and at the same time, spread Chinese culture all over the world.
