[3] The line officially re-entered service on 25 April 2021, becoming Taiwan's fifth rapid transit system in operation.

Then, it follows Wenxin Road along Taichung's 7th Redevelopment Zone, passing through Xitun and Nantun districts and forming a wide semicircle around the city center.

[5][6] A metro system in Taichung was discussed since 1990, which would connect various suburbs including Caotun, Zhongxing New Village, and others.

A new proposal was renewed and approved in 2004, but construction did not begin immediately because of costs exceeding estimates and disagreements over where stations would be.

[8][9][10] In 2010, preliminary work began by relocating trees on the median and rerouting the utilities that run under those roads.

Because of the delays, mayor Jason Hu and his administration were heavily criticized by rivaling political parties.

[16][17] Then, on 10 April 2015, a crane's arm snapped while lifting a 209-ton I-beam, causing the beam to fall and crushing a car underneath.

[24] On 24 August 2020, the Taichung City Council decided to use Hanyu Pinyin for all stations except for Sihwei Elementary School.