II. The New Sea Route of the South China Sea and the Landmark for the Overseas Countries

After the Eastern Han dynasty was overthrown, China came to a period referred to as the Six Dynasties, short for "Six Dynasties of Wu and Jin" which was an abbreviation for Eastern Wu of the southern powerduring the Three Kingdoms Period, Jin (Western Jin and Eastern Jin), Song, Qi, Liang and Chen dynasties of the Southern Dynasties. During this period, the southern regime was confronting the north;as a result, it placed more emphasis on expansion at sea. With the development and accumulation of marine technology and ship-building skills, a new sea route was opened up, starting from Guangzhou, going across the eastern sea of Hainan Island and Xisha Islands to other states in the South China Sea, and then through the Strait of Malacca, to the Indian Ocean, the Red Sea, and on to the Persian Gulf.

In the 1970s, on the northern reef of Xisha Islands, archaeologists of Guangdong Province found the relics of porcelain made in Guangdong in the Southern dynasty. The porcelain belonged to the relics of the shipwrecks, which shows that at that time, merchant ships were able to travel in deep water from Guangdong to the countries in Southeast Asia. After going through the Indian Ocean, the sea route extended westward to the Arabian Peninsula.

During the Southern Dynasties, South China had maintained relatively close official relation with various countries in Southeast Asia. Guangzhou was the starting point of the sea lanes in the South China Sea.The Book of Jin on introduces a country called Linyi,saying that this country was 3000 li away from Nanhai.Linyi was located in what is now central Vietnam. Nanhai referred to Nanhai Prefecture which is called Guangzhou today. According to the accounts on Langkasuka State and Bali, in the Book of Liang, Langkasuka State was 24, 000 li away from Guangzhou and it took two months from Bali to Guangzhou. Langkasuka State is situated today on the Malay Peninsula in Thailand. The earlier location of Bali is disputed: some hold that it was Kalimantan, and others think that it was Bali; both locations are in Indonesia today.

Historiography shows Guangzhou as a landmark measure of distance between China and other countries; sailors setting sail from Guangzhou kept a log of their voyages between Guangzhou and their destinations and, subsequently, local officials would send the log to the government. This practice continued up to the Song dynasty. In Report from Lingnan written by Zhou Qufei, Guangzhou was still used as the navigational coordinate between China and overseas countries.