Originally built in 1913, the Capital Library of China is one of the earliest founded public libraries with about 500,000 ancient books, including rare books in 5,200 types and 67,000 volumes. These books come from the allocation or donations from government organizations, cultural agencies, and private collectors, as well as the long-term purchasing and supplement.

In order to protect rare books and make use of them, the Capital Library of China has chosen certain books for digitization with a detailed book list, making the Image Database for Rare Ancient Book in Stock and provides free access to the public. All the books chosen are indexed in the List of Precious Ancient Books in China, and the first 148 digitized books are indexed in the first to the fifth bunch of the List of Precious Ancient Books in China. The digitization of other books is being carried out and will be added to the previous collection once completed.

Readers can search for information in this database with simple search or combined search, using key words such as title, responsibility carrier and so on, and can read the books according to the division of the four classifications (Jing, the classics of Rujia; Shi, the histories of different dynasties;Zi, the works of scholars before the Qin Dynasty; and Ji, the collection of poetry). Readers can also read the scanned pages of those books online to appreciate those rare works with convenience.