The Taipei MetroTamsui Line (formerly the Danshui Line) is a high-capacity underground, at-grade, and elevated line. The right-of-way was originally occupied by the conventional rail Tamsui TRA Line of the Taiwan Railway Administration, which closed in 1988. The 23.2 km route includes 21 stations and the Beitou maintenance depot. Most of the stations along the Tamsui line are built in a traditional Chinese architectural style. Passengers from Tamsui require only 31 minutes to reach Taipei Main Station, where transfers to both the Nangang Line and the Banqiao Line can be made.
The line opened for revenue service on December 25, 1997. On a southbound journey, trains leave from Tamsui and follow the right-of-way of the old Tamsui-Taipei railroad on an at-grade or elevated level through Beitou, Shilin and Yuanshan, after which the line runs underground through to Taipei Main Station. The route then runs through to Chiang Kai-shek Memorial Hall and becomes the Xindian Line or "green line," continuing service to Xindian Station, the southernmost station in the MRT system.
Over the years, the Tamsui Line used different types of rolling stock. From the start, the line used C301 cars. In 1997, the C321 cars were introduced. In 2007, the newest cars, the C371 cars were used, replacing most of the C301 and all C321 cars.