Dangchang County, under the jurisdiction of Longnan City, Gansu Province, is located in the south of Gansu Province and the northwest of Longnan City, bordering Li County in the east, Zhouqu County and Diebu County in Gannan Prefecture in the west, Wudu District in the south, and Min County in Dingxi City in the north. The whole county covers an area of 3331 square kilometers, including 11 towns, 14 townships and 336 administrative villages. As of November 2020, the permanent population of Dangchang County was 254900.

Dangchang County is located at the edge of the Qinghai-Tibet Plateau and the intersection of the branches of the West Qinling Mountains and Minshan Mountains, with an altitude of 1138-4154 meters and an average annual temperature of 9.3 ℃. It is a temperate continental climate zone. Weiwu Expressway passes through Hadapu Town, Dangchang County, Lianghekou and Shawan Town. Lanzhou-Chongqing Railway runs through Dangchang County.

In 2020, Dangchang County will achieve a GDP of 3.078 billion yuan, a fixed asset investment of 1.385 billion yuan, a large-caliber fiscal revenue of 280 million yuan, a per capita disposable income of 25600 yuan for urban residents, and a per capita disposable income of 7666 yuan for rural residents.