During the Warring States Period, Zou Yan of Qi (240 BC, 305 BC) proposed to divide the world into 8 1 states, with each Kyushu as a group. China is in "Chixian God". State "and divided into Kyushu, namely the little Kyushu. There is a "blue sea" around Kyushu. In addition, there is the Great Yinghai Sea that wraps Kyushu. Here, we can understand Blue Sea and Daying Sea as two geographical concepts, which are very similar to the present sea and ocean. In particular, the concept of blue sea has always been a general term for the marginal sea of China by Hengdai. Later, according to the orientation, the waters around Zero County Shenzhou were called East China Sea, West Sea, South China Sea and North Sea in turn. The East China Sea generally refers to the waters east of China, especially the waters east of the Yellow River Estuary, including the Bohai Sea and the Yellow Sea. As for the Bohai Sea, it was also called Bohai Sea, Bohai Sea, Liaohai Sea in ancient times, and in some cases it was also called Beihai. The scope of the South China Sea includes today's East China Sea and Henghai Sea, and even the Beibu Gulf is among them. But in ancient times, today's South China Sea was more called "the rising sea", and its name appeared as early as the Book of the Later Han Dynasty written by the Jin Dynasty. The name Zhang Hai is also used to refer to islands in the South China Sea. As for the North Sea, Lake Baikal, Lake Balkhash and Caspian Sea in the north of China were once considered as the North Sea. Some scholars believe that the ancient West Sea may refer to the present Arabia, the Red Sea or the Mediterranean Sea in the west of China.