[12] Line S1 is part of Beijing's attempts to tackle environmental problems caused by heavy car use, coal burning and fast urbanization by upgrading its urban rail systems.

Line S1 was envisioned to reuse the Jingmen Railway connecting Cishousi station to Mentougou District.

[14] The line was completed west of the Yongding River on March 31, 2017,[15] and the initial section from Jin'anqiao to Shichang opened on December 30, 2017.

[16] When the Line S1 originally opened in 2017, it was not connected to the rest of the subway network.

In July 2021, a major bridge was completed, and the opening of the extension to Pingguoyuan planned for the end of the year.