The line starts at Nanshijiao in Zhonghe, passes through central Taipei, then splits into two branches: one to Huilong via Xinzhuang and one to Luzhou.

Due to heavy traffic for residents in the districts of Luzhou and Sanchong travelling in and out of central Taipei, a metro line was planned to meet this urgent need.

The tunnels running through Zhonghe-Yonghe area had to pass under narrow streets, skyscrapers and crowded blocks, with limited spaces for stations above ground.

As a result, the whole neighborhood traffic had its so-called "Dark Ages" when the cut-and-cover method was used for station platforms, concourses and crossovers during the 1990s.

[3] Since the line opened for service on 24 December 1998, it has been the most important access to downtown Taipei for nearly half a million of commuters who live in the district.

On 18 December 2011, the 8.2 km (5.1 mi) Daqiaotou to Fu Jen University section passed final inspections by the Ministry of Transportation and Communications.