Abstract: [Purpose/Significance] Chinese ancient books are one of the most important carriers to condense the essence of Chinese traditional culture. However, scholars have found that the database of Chinese ancient books only provides book metadata, which can only meet the basic retrieval and use needs of users, but does not dig and utilize Chinese ancient books in depth from the perspective of knowledge organization. The research in digital humanities is in the ascendant, providing an important modern scientific and technological means for the realization of knowledge correlation of Chinese ancient books. The research on the content mining and knowledge correlation of Chinese ancient books will help to improve the development level and service quality of Chinese ancient books, and promote the creative transformation and innovative development of Chinese excellent traditional culture. [Method/Process] Through literature review and online investigation, this paper summarizes the research of Chinese ancient books' knowledge correlation from the perspective of digital humanities. Based on the research, this paper discusses the differences between traditional database and digital humanistic platforms of Chinese ancient books. First, the organization mechanism is different, and the latter has more diverse and in-depth functions. Second, the scope of collection is expanded. The latter includes not only the original documents, but also the analytical texts and extended documents of ancient books, etc. In the past, most database platforms were "digital" platforms; The digital humanistic platform of Chinese ancient books is a platform of "data", which has been upgraded from "storage" to "analysis" and "correlation". Then, the key links of Chinese ancient books' knowledge correlation are discussed, and the barriers of knowledge correlation are analyzed by examples. [Results/Conclusions] From the perspective of digital humanities, collation of Chinese ancient books has developed from document units to knowledge units by using the data analysis technology, machine learning, visualization technology, etc. The realization of knowledge correlation of Chinese ancient books starts from document organization, based on ancient book data, and its essence is knowledge organization. Knowledge correlation of Chinese ancient books can be used for local chronicles and genealogy mining, seal knowledge network discovery, research context and communication analysis of scholars in specific periods and regions. However, the current knowledge correlation of ancient books still faces barriers such as the difficulty of knowledge element processing, high technical requirements and the lack of integrated platforms in its implementation. Limited by the research conditions, this paper only discusses the research and application, key links and barriers of ancient books' knowledge correlation from a theoretical point of view. In the future work, we will take the opportunity of optimizing and upgrading our ancient books' knowledge platform, to further study the metadata description specification, text conversion and content mining of Chinese ancient books, data exchange and update mechanism among different platforms.

Key words: collation of ancient books, digital humanity, knowledge correlation, knowledge units