The original route, abandoned in 1995, was one of the few 762 mm (2 ft 6 in) narrow-gauge railways in South Korea.

However, since December 28, 2004, the Suin Line is being reconstructed with standard gauge and double tracking as an integral part of the Seoul Metropolitan Subway network and is opening in three phases.

Platforms at stations are built for 8 cars in preparation for the merging of the Bundang Line with the Suin Line, and are prepared for 10 cars when the extension occurs.

2012: 2014: 2016: 2017: 2020: Hagik station is planned to open between Songdo and Inha University in 2020.

In addition, a connection line is under consideration at Suwon that will allow KTX trains to run between the Gyeongbu high-speed railway and Incheon Station via the Suin-Bundang Line by 2025.