In 2002, in preparation for the 2008 Beijing Olympics, it was proposed that the first section of Line 9 should be built between Baishiqiao and Beijing West Railway Station. The entire length of the proposed line was 5.8 kms. However the line only started construction in April 2007 making an opening before the Olympics impossible.
On December 31, 2011, the 11.1 km, 9 station southern section from Guogongzhuang to Beijing West Railway Station opened. At the time it was only connected to the Fangshan Line, meaning demand for its service was very limited.
A year later, the original northern section from Beijing West Railway Station to the National Library entered into operation; but it wasn’t until yet another year had passed that the transfer for Lines 1 to 9 was completed at the Military Museum Station. This finally connected Line 9 and the Fangshan Line to the rest of the subway network and made all major Beijing train stations accessible by subway.
In 2021 it was announced that there would be some through service between Line 9 and the Fangshan line, similar in concept to Line 4 and the Daxing Line, which nowadays effectively operate as one line.
Line 9 was originally proposed to be extended further north and west to Haidian Shanhou, but the proposal was abandoned in favour of the construction of Line 16.
Line 9 has applied a variety of energy-saving technologies, such as the new air-conditioning system adopted in some stations which can reduce energy consumption of air-conditioning in summer; the all-electric braking and regenerative braking of trains save energy and reduce energy consumption; "energy-saving slopes" are set at both ends of the station, so that the train goes uphill before entering the station and downhill after leaving the station, reducing the energy required for braking, and the total length of the energy-saving slope reaches 45.8% of the length of the entire line; the entire line adopts comprehensive water-saving technology, whereby a cooling water pump saves more than 40% energy than other lines; solar water heating is used in the depot.
Line 9 has little to commend it in the way of art. At some stations a simple design of coloured squares on a light blue background adorns the walls of the lift shafts, to help make them stand out.
The decoration of Line 9 stations is mainly based on high efficiency. A part of the grid of each station is coloured with each station being different. This colour is also applied to the entrances and exits to achieve the purpose of "one station, one scene".
Baishiqiao South Station to Liuliqiao East Station are mature urban areas with warm red tones; Qilizhuang Station to Fengtai South Road Station are mainly residential areas with yellow-green tones; Keyi Road Station to Guogongzhuang Station are located in Fengtai Technology Garden and feature blue-violet tones.
Apart from that there are just six stations that display any kind of artwork at all...
National Library
Baishiqiao South
Baiduizi
Military Museum
Fengtaidongdajie
Fengtai Science Park