Library catalogue is a tool to prompt and retrieve the collected documents. Prompt documents include record documents and report documents. Document description is to accurately describe the content and formal characteristics of documents through various items, provide readers with bibliographic knowledge about various documents and help them understand the contents of collected documents; Reporting documents refers to publicizing and reporting related documents to readers according to a certain problem and a certain compiling purpose. Readers can retrieve the collected documents through the library catalogue. The first is the identification of documents, that is, through the contents and structural forms of various items, readers can identify and confirm the documents. Then literature retrieval, that is, through the concentration and combination of items, provides readers with ways to choose and obtain literature from the aspects of subject owner, theme and classification.

The basic feature of library catalogue is to reflect the collected documents. It reflects the scope of literature collection and has two meanings: in a narrow sense, it refers to the literature collection of the library; In a broad sense, it refers to the literature collection of a library and the literature collection of libraries in a region (or country) or even several regions (or countries). From the development trend, due to the emergence of electronic computers, machine-readable catalogs have emerged. Through online retrieval, documents of various countries can exchange needed goods, establish lending relationship and realize resource sharing. Then this collection catalogue is far from a museum or several museums, but a "collection" of different countries and regions. It is impossible for any library to collect all the documents, ancient and modern, Chinese and foreign. In order to solve the contradiction between the limitation of literature collection and the extensiveness of readers' needs to the greatest extent, we should further reflect the literature collected by other libraries through various collection catalogues as far as possible on the basis of correctly reflecting the literature of our library. This can not only answer whether a certain document is collected by our library, but also further answer whether other libraries collect it.