Line 1 runs underneath Chang'an Avenue, the city's grand east–west thoroughfare, right through the heart of Beijing with stops on either side of Tiananmen Square.

The opening of the first phase of the parallel Line 6, caused an 8.46% decrease in daily demand and a 10-20% reduction in peak flow during rush hour.

The line heads southeast to its second stop at Gucheng and from there runs straight east, following Chang'an Avenue all the way to its eastern terminus, Sihuidong in Chaoyang District, just beyond the 4th Ring Road.

[7] ● Normal: Gucheng — Huanqiu Dujiaqu (Universal Resort) ● Morning rush hour: Gongzhufen — Guoyuan ● Evening rush hour: Gucheng — Guoyuan The first section of subway in Beijing officially started trial operation on January 15, 1971.

It was 10.7 km (6.6 mi) long and ran between Beijing railway station to Gongzhufen,[b] which today is a section of Line 1 and 2.

[17] Since 2014, the signaling and power systems has been gradually upgraded to allow for trains to run more frequently.

[25] However, the Beijing Subway responded that Line 1's and Batong's signal systems are completely different, so through-operation will be more difficult to achieve, from an engineering standpoint.

Beyond Pingguoyuan, Line 1 extends further northwest where it has several other stations: Gaojing (高井) and Fushouling (福寿岭).

[28][29] A proposal to open the Gaojing station to public is mentioned within 2022 and 2023 working plan of the Shijingshan District.

[28][30] Due to Line 1's severe overcapacity problem, there are plans to introduce 7-car or longer trains.

In order for this plan to proceed the oldest section of Line 1 between Pingguoyuan and Nanlishi Lu, which only has platforms long enough to accommodate 6-car trains, will need to be lengthened.

The newer section between Fuxingmen and Sihuidong, formerly known as "Fuba line" during construction, has platforms long enough for 8-car trains.

[35] To facilitate construction of the extension, the project will need to renovate and expand Bajiao Amusement Park Station.