The most recent extension is the central section from National Art Museum to Zhushikou, opened on 31 December 2021.

Apart from the Zhuxinzhuang station and an 1.7 km (1.056 mi) section of elevated track leading therefrom, the entire line runs underground.

[4][5] The first section of Line 8 to be built was the four-station segment from Beitucheng to Forest Park South Gate, 4.35 km (2.703 mi) in length, that serves the Olympic Green.

[13] The Lincuiqiao station, just west of the Olympic Forest Park, was originally planned as an emergency stop, but was added at the behest of nearby residents and their municipal people's congress representative, Tian Yuan, who argued that the 5.1 km (3.169 mi) gap between South Gate of Forest Park and Yongtaizhuang made subway access inconvenient for residents along Lincui Road.

[16] On December 28, 2013, Line 8 reached 26.614 km (16.537 mi) in length with the opening of the Changping-Line 8 Connector and the southern extension to Nanluoguxiang.

[17] The Changba Connector contains three stations: Pingxifu, Yuzhilu and Zhuxinzhuang, and forms the northernmost section of Line 8.

[20][21] In Phase III & IV, Line 8 will be extended further south from the National Art Museum through Qianmen and Yongdingmen to beyond the southern 5th Ring Road.

[22] Plans of Line 8 in Phase III & IV showed 16 stations for 21.0 km (13.0 mi).

Phase III was scheduled to be built by 2015[24] but the commencement of construction was not set to begin until October 2013.

[20][21] The section between National Art Museum and Zhushikou, which includes 3 stations (Jinyu Hutong, Wangfujing and Qianmen) opened on 31 December 2021.

[27][28] A further southern extension from Yinghai to the China-Japan Innovation Cooperation Demonstration Zone is under planning.