The research on the history of East Asian ancient currencies has been long receiving attention from domestic and overseas scholars. The studies of the history of the currency in individual countries of the East Asian region have attained a great amount of achievements, while the studies of the international currency among countries in East Asian mainly focus on the overseas distribution of Chinese currency during the Song and Ming dynasties; there is very few studies that discuss the common currency in the East Asian region during the Sui and Tang dynasties. In the period of Sui and Tang dynasties, the East Asian Community, which was built on the interaction of tribute and investiture between imperial dynasty and other peripheral countries, on the one hand exhibited its distinguished political or diplomatic feature; on the other hand it possessed a strong aspect of cultural exchange. What’s more, it also showed a marked characteristic of official trade. As far as envoys dispatched from Imperial China to foreign countries and missions between Bo Hai, Silla and Japan are concerned, which kind of currency was used to facilitate trading? The answers to this question provided by the previous studies are unconvincing. A popular view in the academia of Japan is: since the beginning of the 8th century, the Japanese envoys to Tang China had already brought gold on them as currency to consume in Imperial China, and it hence left the impression on the Tang Dynasty people that Japan had large gold reserves. Even, this impression was passed on to the Islamic businessmen by Tang People, and caused the prevalence of the saying ′al-Wāqwāq′ (the country of gold) in Asian in the 9th Century. Was Japan rich in gold in ancient time? Was Gold the common currency in the East Asian Region back to the 8th century? The answers to these questions remain unclear. Firstly, it is until 749 A.D. that gold reserve was first discovered in Mutsu, Japan. Emperor Shomu stated clearly in imperial edicts that gold came from other countries since the creation of the world, and Japan never produced gold. Therefore, it is impossible that the Japanese missions to Tang China carried gold. On the contrary, Japanese envoys to Tang China even undertook the task of buying gold. Secondly, according to the records of the Jiu Tang Shu, Zhang Zhuo was a prestigious literate, the embassies from Japan and Silla to Tang China would purchase his works with ″gold″ every time when they were in China. It needs to note that ″gold″ here is not merely the gold currency; rather, ″gold″ should be interpreted as the general name of all forms of currency. Back then, there was no gold production in Japan, and the money given by the Silla court to Silla students in Tang China to buy books was called ″book-purchasing silver.″ Half century after the discovery of gold in Japan, the production in Mutsu could barely meet Japan’s domestic demand hence it could not be employed as currency in international trading. For the whole 8th century, the common currency in East Asian was ″silk.″ Engishiki documents the currency given by the Japanese court to the envoys to Tang China, Bo Hai and Silla is ′silk,′ which includes ′shi(絁)′ ′mian(绵)′ and ′bu（布）.′ The fact that silk was the international currency form used in East Asian can be attributed to the threefold tax system of grain, cloth and corvee labour, which was held by Tang Empire and adapted by Japan and Silla. Silk had been used as the common currency in East Asian countries for a long time. However, the drawback of this form of currency is apparent: the size of silk is large, and it is inconvenient to handle. In 804 A.D., for the first time the Japanese envoys to Tang China used gold rather than silk as currency in China. This replacement is of milestone significance in the history of East Asian international currency. With small size and high value, and with production growing year by year in Japan, gold was brought by envoys, monks and merchants as travelling money for the century afterwards. The image of ′the country of gold′ of Japan was then formed.