Book classification, also called book classification thesaurus, is classified according to the contents, forms, genres and readers' uses. Under the guidance of certain philosophical thoughts, the books of various disciplines are divided into several categories according to their subject contents by using the principle of knowledge classification and logical methods. Each category is divided into many subclasses, and each subclass is divided into molecular subclasses.

Finally, every kind of book can be divided into certain categories, and each category has a category number. Classified thesaurus is a collection of hierarchical classification numbers and categories.

Characteristics of book classification labels:

(1) China Library Classification is a comprehensive classification with detailed categories, many annotations and different versions, which can meet the document classification needs of various libraries and information departments.

(2) On the basis of the rank list, the compilation technology is improved by adopting the combined numbering method, setting alternate categories, compiling multiple sub-tables and adopting multi-column classification.

(3) The classification number is short, easy to remember and use.

(4) A detailed category index and description (manual) has been compiled.

China Library Classification has been adopted by most library and information departments in China. Starting from 1988, the standard book number (ISBN) of books published in China adopts the category number of China Library Classification. Its classification number is also printed on the centralized catalogue cards compiled by Beijing Library and Shanghai Library. 1985 won the first prize of national scientific and technological progress.