The Yunnan-Vietnam Railway was the first to link the province with other countries, running 855 km from Kunming to Haiphong in Vietnam. Because of its narrow gauge, the railway is often called "The 1-meter-gauge railway".

Construction of the Vietnamese section began in 1901 and was completed in 1903. The Yunnan section was finished in 1910, and its 425 bridges and 155 tunnels, accounted for 36 percent of its total length. The line began at Kunming North Railway Station and ran to Hekou, via towns such as Yiliang, Kaiyuan, Mengzi and Pingbian.

In 1940, Japanese soldiers invaded Vietnam and bombed the railway. To prevent the Japanese from moving north into Yunnan, the order was given to destroy Hekou Bridge, which connected Yunnan and Vietnam at the time. Some parts of the Yunnan section were also dismantled. The original rails were later used for the Kunming-Qujing railway that carried the international military supplies on the Yunnan-Myanmar Road and the Hump Flights.