At present, there are five main methods of document classification in China: China Law, a Chinese library book classification, was initiated by Beijing Library. Published in 1975, * * * is divided into 5 basic categories and 22 major categories. Marks are mixed numbers of Chinese phonetic alphabet and Arabic numerals, which are arranged strictly in decimal system. China Library Classification was compiled by China Institute of Science and Technology Information and other units on the basis of China Law, with the publication number of 1975. Buildings and symbols are basically the same as the laws of China. The library classification of China Academy of Sciences is referred to as "Ketu method". Edited by Library of China Academy of Sciences, published in 1958. * * * It is divided into five parts and 25 categories, with Arabic numerals as labels and two parts as numbers: the serial numbers of the major categories and their main categories are 00-99, and the fine categories are decimal. The book classification of Renmin University of China Library is referred to as NPC Law for short, compiled by Renmin University Library and published by 1953. It is divided into four categories: 17, and the figures are Arabic numerals. The International Book Integration Classification is a new book classification compiled by Hu Changzhi of Wuhan University of Technology Library under the background that the classification at home and abroad is in trouble. The author analyzes the shortcomings of Chinese Library Classification from theory to application, and advocates taking formal logic as the theoretical basis of book classification. This paper puts forward some breakthrough dividing thinking and sorting techniques, such as the law of document inheritance and interdisciplinary positioning, which opens up a new way for the transformation of book classification from professionalism to popularity.