Donghai County, subordinate to Lianyungang City, Jiangsu Province, is located in the northeast of Jiangsu Province, bordering Haizhou District, Lianyungang City in the east, Maling Mountain in the west, Shuyang County and Guanyun County in the south, and Ganyu District, Lianyungang City in the northeast along the Xinshu River. It is known as the crystal capital of the world and the hometown of hot springs in China. With a total area of 2040.9 square kilometers and a population of 1.24 million, it has jurisdiction over 19 towns (farms), 2 streets, 1 provincial economic development zone, 1 provincial high-tech zone and 1 provincial tourism resort. According to the data of the seventh population census, as of 0:00 on November 1, 2020, the permanent population of Donghai County was 1047357.

The East China Sea is famous for its crystal stones. Donghai Crystal, a product approved for the protection of national geographical indications, is from the East China Sea. The existing "Crystal King" weighing 4.35 tons in the China Geological Museum is from the East China Sea. Chairman Mao's crystal coffin is also refined from the East China Sea Crystal. Donghai Hot Spring is located at the south foot of Yushan Mountain, with a geothermal area of 2.4 square kilometers, and is known as the "No.1 Hot Spring in East China". The East China Sea enjoys the reputation of "the county of hundreds of lakes". Three lakes, including Xishuanghu Lake, are connected by the Jade Belt River.

The East China Sea has a long history. Qu County was set up in the Qin Dynasty. In the first year of the Republic of China (1912), Haizhou Zhili Prefecture was changed into Donghai County, and the county seat was set in the current Haizhou City. Daxianzhuang Site, Quyang Ancient City, Yinwan Han Tomb, and Maling Ancient Road have inherited human civilization for 50000 years. He has successively cultivated historical and cultural celebrities such as Bao Zhao, the poet of the Southern Dynasty, Zhu Lu, the crown prince of the Qing Dynasty, Zhu Ziqing, the modern essayist, and Yan Han, the contemporary printmaker. Donghai County has successively won the honors of National Advanced County in Grain Production, National Advanced County in Science and Technology Progress Assessment, National Health County, National Ecological County, National Advanced County in Culture, and National Advanced County in Mass Sports.

In 2021, the GDP will reach 63 billion yuan, up 10% year on year; The general public budget revenue exceeded 3 billion yuan, an increase of 21.6%, ranking first in counties (cities) in the province; Total imports and exports increased by 23%; The actual utilization of foreign capital is 120 million US dollars.