The classification number of China Library Classification is determined by the control standard compiled by the Ministry of Industry and Information Technology. According to the classification content and system structure, books are divided into eight categories, and the corresponding numbers are: A, B, C, D, E, F, G, H. Then, each category is followed by four digits and ***28 classification numbers, and each category uses a number to indicate the genre of books.

The China Library Classification basically adopts the layered numbering system. That is, according to different grades of categories, numbers with different digits are given. The first category uses one symbol, the second category uses two symbols, the third category uses three symbols, and so on.

The history of classification and numbering of China library.

China Library Classification is a representative large-scale comprehensive classification compiled and published after the founding of the People's Republic of China, and it is the most widely used classification system in domestic libraries today. The first edition of China Library Classification was published in 1975, and the fourth edition was published in 1999. The fourth edition of the revised China Library Classification has added the category of classified materials, which is distinguished from the category of classified books by a "+",so it was officially renamed as China Library Classification, with the abbreviation unchanged.

The fourth edition of Library Classification of China comprehensively supplements new themes, expands the category system, and makes the classification keep pace with the development of science and technology. At the same time, standardize categories, improve the reference system and annotation system, adjust the category system, and add sub-tables, so as to obviously strengthen the expansion of categories and the accuracy of classification.