Changhai County, a county under the jurisdiction of Dalian City, Liaoning Province, is located in the Changshan Islands, an extension of the Changbai Mountains, a warm temperate semi humid monsoon climate, with four distinct seasons, warm winter and cool summer, sufficient sunshine and small temperature difference; The total land area is 142 square kilometers, governing 5 towns.

According to the data of the seventh census, as of 0:00 on November 1, 2020, Changhai County has 66,824 permanent residents.

Changhai County is the only island border county in northeast China. It is located in the northern sea area of the Yellow Sea on the east side of Liaodong Peninsula, facing the Korean Peninsula in the east, facing the Shandong Miaodao Islands in the southwest, and adjacent to the urban area of Dalian, Pulandian District and Zhuanghe City in the west and north. It is the nearest area in the northeast to Japan and South Korea. In November 2018, Changhai County was selected as one of the "100 Happy Counties" in China.

In 2018, Changhai County achieved a GDP of 9.45 billion yuan, which is 2.3% lower than that of the previous year (constant price, the same below). According to the three industry accounting, the added value of the primary industry was 5.03 billion yuan, up 4.3%; The added value of the secondary industry was 780 million yuan, down 2.6%; The added value of the tertiary industry was 3.64 billion yuan, down 10.9%.

In July 2020, it won the honorary title of National Health County in 2017-2019.