Chongming Island is the product of the development of the new Yangtze River Delta, and its birthplace is the shallow sea outside the Yangtze River estuary. When the Yangtze River rushes eastward and flows into the estuary area, a large amount of sediment is gradually deposited here due to the decrease of the specific gradient and the slow flow rate. On the one hand, the coastal plain is formed on the north and south banks of the Yangtze River estuary, and on the other hand, scattered estuary sandbars are formed in the river channel. In this way, Chongming Island has gradually become a typical estuary sand island. It has experienced more than 1000 years of ups and downs from the surface to the final formation of the big island.

From 6 18 to 626 (during the reign of Tang Wude), two sandbars rose in the water south of Dongbuzhou (now Lvsi area). Two continents separated by more than 70 miles of water are named Dongsha and Xisha (also known as Gu Junsha), which is the predecessor of the island. 1025 (the third year of Song Tiansheng), Yao continued to rise in the northwest of Dongsha (named after Yao and Liu's ancestors), bordering Dongsha. 110/year (Song Jianzhong, Jing Guoyuan), Sansha rises in the northwest of Yaoliusha (named after three overlaps; He also said that it was named after Zhu, Chen and Zhang.

127 1 ~ 1368 (Yuan Dynasty), the sands above 10, such as qianying sand, Matuo sand and Zhangpu sand, rose one after another. At the end of Yuan Dynasty and the beginning of Ming Dynasty, Dongsha collapsed, Xisha collapsed, Sansha rose in the north, and Yaoliusha collapsed in the south and rose in the north, gradually connecting with Sansha. From 1399 to 1644 (from the early Ming Dynasty to the late Ming Dynasty), more than 30 sandy lands, such as Maanshan, Chenensha, Gaomingsha, Xiaoyinsha, Changsha, Yuanjiasha, Xiangsha and Gaotousha, were successively raised. From 1522 to 1722 (from the early years of Jiajing in Ming Dynasty to the late years of Kangxi in Qing Dynasty), sand swelled and collapsed frequently. Yaoliusha and Sansha collapsed, Xisha, Chenensha and Fanliansha fell into the water one after another, Pingyangsha rose first and then collapsed, while Changsha rose to pieces with Yuanjiasha, Wujiasha, Xiangsha and Nansha around it with the collapse of Pingyangsha. Around 1644 (late Ming and early Qing Dynasty), Chongming Island started from Gaotousha in the east and reached Pingyangsha in the west, becoming a big island with a length of 200 li and a width of 40 li.