Yanjin County is under the jurisdiction of Zhaotong City, Yunnan Province. Located at 103 east longitude ? 59′18 ?~ one hundred and four ? 27′50 ?、 27 N ? 49′11 ?~ twenty-eight ? 24′38 ? between. It is located at the junction of Yunchuan in northeast Yunnan, in the middle of Zhaotong and Yibin, bordering Junlian, Gaoxian and Xuzhou District in Sichuan in the northeast, Yiliang in Yunnan in the south, Daguan, Yongshan and Suijiang in Yunnan in the west, and Shuifu County in the north. The county is narrow from north to south, slightly narrow from east to west, with the maximum longitudinal distance of 62.5 kilometers and the maximum transverse distance of 46 kilometers. The total area is 2091 square kilometers. According to the data of the seventh population census, as of 0:00 on November 1, 2020, the permanent population of Yanjin County was 317463.

It was named after having a salt well to produce salt and a ferry to ferry the flood. It was the residence of Bo people in ancient times. The Xia, Shang and Zhou dynasties belonged to the Liangzhou region, and later changed its affiliation. Kaibian County was established in 587 A.D., and is the seat of the current market town of Tantou Township. In 1727, the land was changed to flow, and Yanjin belonged to the Daguan Hall of Wumeng Prefecture. In 1917, the county was officially established and named Yanjin.

In Yanjin County, there are traces of Qin Kai's "Wuchi Road", "Tang Yuanzi Cliff", "Bo People's Hanging Coffin", "Ancient Castle" and other relics. It is rich in Chinese medicinal materials, with a wide variety of orchids and a high medicinal value of black-bone chicken. Rich in limestone, anthracite and water resources, it is a mountainous county to be developed. On May 17, 2020, Yanjin County withdrew from the poverty county sequence. In August 2021, it was selected as the national key county for rural revitalization.

In 2019, Yanjin County's GDP reached 5.28 billion yuan, up 9.1% year on year; The investment in fixed assets of scale reached 2.39 billion yuan, down 39.6% year on year; The county's general public budget revenue reached 172 million yuan, up 6.6% year on year; The total retail sales of consumer goods reached 1.22 billion yuan, up 9.8% year on year; The per capita disposable income of urban permanent residents reached 28693 yuan, up 7.9% year on year; The per capita disposable income of rural permanent residents reached 10664 yuan, an increase of 11% year on year.